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User talk:168...

I am very sorry 168...Very sorry :-( User:Anthere

I hope you don't let this stop you editing here. Whilst I disagree with your protection of pages you were involved in, I do understand the point you were trying to make. I disagree only with your methods, not your intentions and I hope you'll be back. Angela. 17:00, Mar 8, 2004 (UTC)

I'm sorry that this has happened and I also hope that you will be back. BCorr € Брайен 17:07, Mar 8, 2004 (UTC)

Likewise, me. --Lexor|Talk 17:08, 8 Mar 2004 (UTC)

I agree with the above sentiments. Your contributions here are very valuable. →Raul654 17:17, Mar 8, 2004 (UTC)

[Peak to 168...:] It just occurred to me that your "civil disobedience" campaign to have a certain user "banned" may have been based on some flawed assumptions about certain technicial aspects of a "ban". (In essence, it's not possible to ban a person.) Perhaps if you had understood these limitations, you would have seen the wisdom of the approach that I had argued for and which Anthere has now implemented (community action with sysop support). I am not writing to say "I told you so" but in the hope that you will see that some of your actions were, at least to some extent, based on some flawed assumptions, and that as a result you will cheerfully rejoin the fray.Peak 17:31, 8 Mar 2004 (UTC)

Don't let all this nonsense drive you away. Your contributions to articles are both valued and worthwhile. Allow someone else to fight the idiots, and concentrate on the quality edits that we remember of you. Stewart Adcock 18:26, 8 Mar 2004 (UTC)

I could not agree more with Stewart Adcock's statement. -- Cyan 19:39, 8 Mar 2004 (UTC)

168, I only recently began following disputes on the DNA page, and was just informed that you are leaving Wikipidia. I hope you will reconsider. You and I have had edit conflicts in the past; this is not the time to rehash old feelings but I want to make clear, as I hope it was clear in the past, that I respect your knowledge and have valued your contributions to Wikipedia. I believe very strongly in the importance of a community of Wikipedians; that requires a good deal of compromise and patience on the part of contributors. This is not easy; I think most people -- certainly I -- sometimes fall short. That is why I have strived both to forgive others, and to ask others to forgive me. Sometimes I do not have the energy for this and have simply had to take a break from Wikipedia. I sincerly hope that this is what you are doing, and I hope you will come back to work with us. Slrubenstein

sigh
168, I am very upset to hear of your fate. I disagree 100% with what has transpired. The punishment in no way fits the crime. And there simply is not enough forgiveness in this case. With such injustice, I fear we will fall into a French Revolution scenario, in which everyone goes on trial for trivial things, and the guillotine is invoked on one and all. I suppose we each need to wonder...who's next. You continue to have my support. I value your work and your efforts. Kingturtle 00:27, 9 Mar 2004 (UTC)

Nobody should be happy when the human equivalents of hyper-aggressive bees set up territory here. Actually, I unfairly demean the bees. At least they are protecting a hive that has something of value in it, real honey and not swamp gas. Don't let the hornets win. "French Revolution" is the appropriate simile, I fear. Somehow we have to have a society that sorts out the hornets. P0M 21:25, 9 Mar 2004 (UTC)

After reading up on what has transpired, I agree with Kingturtle and P0M. You seem to have been stripped of your powers by a developer who has now made the same mistake(without causing anyone to bat an eye) that you made. Hopefully this can all be sorted out and you will get your powers back. Keep up the good work and don't let anyone get to you. Perl 00:23, 11 Mar 2004 (UTC)

Mav v. 168...
The request for arbitration in Requests for arbitration/Mav v. 168 was accepted on April 20, 2004. Please present evidence at Requests for arbitration/Mav v. 168/Evidence. Fred Bauder 11:17, Apr 20, 2004 (UTC)

I hope you'll decide to resume contributing here. You're contributions to our articles have been very valuable (I'm thinking of DNA in particular). →Raul654 05:23, Apr 21, 2004 (UTC)
 * I second that. But the way many users treated you earlier this year was shameful, so I can understand your reservations about returning. 172 10:57, 15 Aug 2004 (UTC)

Article Licensing
Hi, I've started a drive to get users to multi-license all of their contributions that they've made to either (1) all U.S. state, county, and city articles or (2) all articles, using the Creative Commons Attribution-Share Alike (CC-by-sa) v1.0 and v2.0 Licenses or into the public domain if they prefer. The CC-by-sa license is a true free documentation license that is similar to Wikipedia's license, the GFDL, but it allows other projects, such as WikiTravel, to use our articles. Since you are among the top 1000 Wikipedians by edits, I was wondering if you would be willing to multi-license all of your contributions or at minimum those on the geographic articles. Over 90% of people asked have agreed. For More Information:
 * Multi-Licensing FAQ - Lots of questions answered
 * Multi-Licensing Guide
 * Free the Rambot Articles Project

To allow us to track those users who muli-license their contributions, many users copy and paste the " " template into their user page, but there are other options at Template messages/User namespace. The following examples could also copied and pasted into your user page:

 * Option 1
 * I agree to multi-license all my contributions, with the exception of my user pages, as described below:

OR
 * Option 2
 * I agree to multi-license all my contributions to any U.S. state, county, or city article as described below:

Or if you wanted to place your work into the public domain, you could replace " " with "  ". If you only prefer using the GFDL, I would like to know that too. Please let me know what you think at my talk page. It's important to know either way so no one keeps asking. – Ram-Man (comment) (talk)  13:53, Dec 9, 2004 (UTC)

Missing Wikipedians
Wikipedia:Missing Wikipedians -- Zondor 09:30, 26 April 2006 (UTC)

Chemical synapse FAR
Chemical synapse has been nominated for a featured article review. Articles are typically reviewed for two weeks. Please leave your comments and help us to return the article to featured quality. If concerns are not addressed during the review period, articles are moved onto the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Remove" the article from featured status. The instructions for the review process are here. Reviewers' concerns are here. LuciferMorgan 17:12, 7 March 2007 (UTC)

Cell membrane
The Cell membrane article received heavy editing today by new/unregistered users, which I noticed at WikiRage.com. The article may benefit from a good review. According to Wikipedia Page History Statistics, you are one of the top contributors to that page. If you have the time, would you please read over the article and make any necessary changes. Thanks. --  Jreferee  (Talk) 08:02, 16 September 2007 (UTC)

Action potential
Action potential has been nominated for a featured article review. Articles are typically reviewed for two weeks. Please leave your comments and help us to return the article to featured quality. If concerns are not addressed during the review period, articles are moved onto the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Remove" the article from featured status. The instructions for the review process are here. Reviewers' concerns are here.

FAR
nominated Action potential for a featured article review here. Please join the discussion on whether this article meets featured article criteria. Articles are typically reviewed for two weeks. If substantial concerns are not addressed during the review period, the article will be moved to the Featured Article Removal Candidates list for a further period, where editors may declare "Keep" or "Remove" the article's featured status. The instructions for the review process are here.  Pyrrhus  16 ''' 18:49, 20 February 2010 (UTC)

Speedy deletion nomination of Entropic

A tag has been placed on Entropic requesting that it be speedily deleted from Wikipedia. This has been done under section A7 of the criteria for speedy deletion, because the article appears to be about an organization or company, but it does not indicate how or why the subject is important or significant: that is, why an article about that subject should be included in an encyclopedia. Under the criteria for speedy deletion, such articles may be deleted at any time. Please read more about what is generally accepted as notable.

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ArbCom elections are now open!
MediaWiki message delivery (talk) 08:52, 23 November 2015 (UTC)

Proposed deletion of Genetic program

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Good article reassessment for Aquaporin
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title: User talk:168...


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9

9 (nine) is the natural number following and preceding.

Evolution of the Hindu–Arabic digit
Circa 300 BC, as part of the Brahmi numerals, various Indians wrote a digit 9 similar in shape to the modern closing question mark without the bottom dot. The Kshatrapa, Andhra and Gupta started curving the bottom vertical line coming up with a -look-alike. How the numbers got to their Gupta form is open to considerable debate. The Nagari continued the bottom stroke to make a circle and enclose the 3-look-alike, in much the same way that the sign @ encircles a lowercase a. As time went on, the enclosing circle became bigger and its line continued beyond the circle downwards, as the 3-look-alike became smaller. Soon, all that was left of the 3-look-alike was a squiggle. The Arabs simply connected that squiggle to the downward stroke at the middle and subsequent European change was purely cosmetic.

While the shape of the glyph for the digit 9 has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in.

The form of the number nine (9) could possibly derived from the Arabic letter و|waw, in which its isolated form (و) resembles the number 9.

The modern digit resembles an inverted 6. To disambiguate the two on objects and labels that can be inverted, they are often underlined. It is sometimes handwritten with two strokes and a straight stem, resembling a raised lower-case letter q, which distinguishes it from the 6. Similarly, in seven-segment display, the number 9 can be constructed either with a hook at the end of its stem or without one. Most LCD calculators use the former, but some VFD models use the latter.

Mathematics
Nine is the fourth composite number, and the first composite number that is odd. Nine is the third square number (32), and the second non-unitary square prime of the form p2, and, the first that is odd, with all subsequent squares of this form odd as well. Nine has the even aliquot sum of 4, and with a composite number sequence of two (9, 4, 3, 1, 0) within the 3-aliquot tree. It is the first member of the first cluster of two semiprimes (9, 10), preceding (14, 15). Casting out nines is a quick way of testing the calculations of sums, differences, products, and quotients of integers in decimal, a method known as long ago as the 12th century.

By Mihăilescu's theorem, 9 is the only positive perfect power that is one more than another positive perfect power, since the square of 3 is one more than the cube of 2.

9 is the sum of the cubes of the first two non-zero positive integers $$1^{3} + 2^{3}$$ which makes it the first cube-sum number greater than 1|one.

It is also the sum of the first three nonzero factorials $$1! + 2! + 3!$$, and equal to the third exponential factorial, since $$9 = 3^{2^{1}}.$$

Nine is the number of derangements of 4, or the number of permutations of four elements with no fixed points.

9 is the fourth refactorable number, as it has exactly three positive divisors, and 3 is one of them.

A number that is 4 or 5 modulo 9 cannot be represented as the sum of three cubes.

If an odd perfect number exists, it will have at least nine distinct prime factors.

9 is a Motzkin number, for the number of ways of drawing non-intersecting chords between four points on a circle.

The first non-trivial magic square is a $$3$$ x $$3$$ magic square made of nine cells, with a magic constant of 15. Meanwhile, a $$9$$ x $$9$$ magic square has a magic constant of 369.

There are nine Heegner numbers, or square-free positive integers $$n$$ that yield an imaginary quadratic field $$\Q\left[\sqrt{-n}\right]$$ whose ring of integers has a unique factorization, or class number of 1.

Polygons and tilings
The regular hexagon contains a total of nine diagonals, and is one of only four polytopes with radial equilateral symmetry such that its long radius (center to vertex length) is the same as the edge-length: (the hexagon), the cuboctahedron, the tesseract, and the 24-cell.

A polygon with nine sides is called a nonagon. Since 9 can be written in the form $$2^m3^np$$, for any nonnegative natural integers $$m$$ and $$n$$ with $$p$$ a product of Pierpont primes, a regular nonagon is constructed with a regular compass, straightedge, and angle trisector. Also an enneagon, a regular nonagon is able to fill a plane-vertex alongside an equilateral triangle and a regular 18-sided octadecagon (3.9.18), and as such, it is one of only nine polygons that are able to fill a plane-vertex without uniformly tiling the plane. In total, there are a maximum of nine semiregular Archimedean tilings by convex regular polygons, when including chiral forms of the snub hexagonal tiling. More specifically, there are nine distinct uniform colorings to both the triangular tiling and the square tiling (the simplest regular tilings) while the hexagonal tiling, on the other hand, has three distinct uniform colorings.

The fewest number of squares needed for a perfect tiling of a rectangle is nine.

Polyhedra
There are nine uniform edge-transitive convex polyhedra in three dimensions:
 * the five regular Platonic solids: the tetrahedron, octahedron, cube, dodecahedron and icosahedron;
 * the two quasiregular Archimedean solids: the cuboctahedron and the icosidodecahedron; and
 * two Catalan solids: the rhombic dodecahedron and the rhombic triacontahedron, which are duals to the only two quasiregular polyhedra.

Nine distinct stellation's by Miller's rules are produced by the truncated tetrahedron. It is the simplest Archimedean solid, with a total of four equilateral triangular and four hexagonal faces.

Collectively, there are nine regular polyhedra in the third dimension, when extending the convex Platonic solids to include the concave regular star polyhedra known as the Kepler-Poinsot polyhedra.

Higher dimensions
In four-dimensional space, there are nine paracompact hyperbolic honeycomb Coxeter groups, as well as nine regular compact hyperbolic honeycombs from regular convex and star polychora. There are also nine uniform demitesseractic ($$\mathrm D_{4}$$) Euclidean honeycombs in the fourth dimension.

There are only three types of Coxeter groups of uniform figures in dimensions nine and thereafter, aside from the many families of prisms and proprisms: the $$\mathrm A_{n}$$ simplex groups, the $$\mathrm B_{n}$$ hypercube groups, and the $$\mathrm D_{n}$$ demihypercube groups. The ninth dimension is also the final dimension that contains Coxeter-Dynkin diagrams as uniform solutions in hyperbolic space. Inclusive of compact hyperbolic solutions, there are a total of 238 compact and paracompact Coxeter-Dynkin diagrams between dimensions two and nine, or equivalently between ranks three and ten. The most important of the last ${\tilde{E}}_9$ paracompact groups is the group $${\tilde{T}}_9$$ with 1023 total honeycombs, the simplest of which is 621 whose vertex figure is the 521 honeycomb: the vertex arrangement of the densest-possible packing of spheres in 8 dimensions which forms the $\mathbb E_{8}$ lattice. The 621 honeycomb is made of 9-simplexes and 9-orthoplexes, with 1023 total polytope elements making up each 9-simplex. It is the final honeycomb figure with infinite facets and vertex figures in the k21 family of semiregular polytopes, first defined by Thorold Gosset in 1900.

In base 10
9 is the highest single-digit number in the decimal system.

Occurrence
9 is related to just 3, 6 and itself. When we do the doubling of all natural numbers we get, 1, 2, 4, 8, 16, 32, 64... Now if we try to get the digital roots of two digit numbers, then, 16= 1+6 =7. 32= 3+2 =5. Such way, only 1, 2, 4, 5, 7, 8 occur. Same thing happens when we start halving the numbers.

Nikola tesla
Nikola Tesla was a great scientist. Despite his work on free energy etc. he stated, " If the understand the numbers 3, 6, 9, you understand the universe."

Divisibility
A positive number is divisible by nine if and only if its digital root is nine:
 * 9 × 2 = 18 (1 + 8 = 9)
 * 9 × 3 = 27 (2 + 7 = 9)
 * 9 × 9 = 81 (8 + 1 = 9)
 * 9 × 121 = 1089 (1 + 0 + 8 + 9 = 18; 1 + 8 = 9)
 * 9 × 234 = 2106 (2 + 1 + 0 + 6 = 9)
 * 9 × 578329 = 5204961 (5 + 2 + 0 + 4 + 9 + 6 + 1 = 27; 2 + 7 = 9)
 * 9 × 482729235601 = 4344563120409 (4 + 3 + 4 + 4 + 5 + 6 + 3 + 1 + 2 + 0 + 4 + 0 + 9 = 45; 4 + 5 = 9)

That is, if any natural number is multiplied by 9, and the digits of the answer are repeatedly added until it is just one digit, the sum will be nine.

In base-$$N$$, the divisors of $$N - 1$$ have this property.

Multiples of 9
There are other interesting patterns involving multiples of nine:
 * 9 × 12345679 = 111111111
 * 18 × 12345679 = 222222222
 * 81 × 12345679 = 999999999

The difference between a base-10 positive integer and the sum of its digits is a whole multiple of nine. Examples:
 * The sum of the digits of 41 is 5, and 41 − 5 = 36. The digital root of 36 is 3 + 6 = 9.
 * The sum of the digits of 35967930 is 3 + 5 + 9 + 6 + 7 + 9 + 3 + 0 = 42, and 35967930 − 42 = 35967888. The digital root of 35967888 is 3 + 5 + 9 + 6 + 7 + 8 + 8 + 8 = 54, 5 + 4 = 9.

If dividing a number by the amount of 9s corresponding to its number of digits, the number is turned into a repeating decimal. (e.g. $\overline{285714}$ = 0.274274274274...)

Another consequence of 9 being 10 − 1 is that it is a Kaprekar number, preceding the ninth and tenth triangle numbers, 45 and 55 (where all 9, 99, 999, 9999, ... are Keprekar numbers).

Six recurring nines appear in the decimal places 762 through 767 of $\pi$. (See six nines in pi).

Alphabets and codes

 * In the NATO phonetic alphabet, the digit 9 is called "Niner".
 * Five-digit produce PLU codes that begin with 9 indicate organic foods.

Indian culture
Nine is a number that appears often in Indian culture and mythology. Some instances are enumerated below.
 * Nine influencers are attested in Indian astrology.
 * In the Vaisheshika branch of Hindu philosophy, there are nine universal substances or elements: Earth, Water, Air, Fire, Ether, Time, Space, Soul, and Mind.
 * Navaratri is a nine-day festival dedicated to the nine forms of Durga.
 * Navaratna, meaning "nine jewels" may also refer to Navaratnas – accomplished courtiers, Navratan – a kind of dish, or a form of architecture.
 * In Indian aesthetics, there are nine kinds of Rasa.

Chinese culture

 * Nine (九; ) is considered a good number in Chinese culture because it sounds the same as the word "long-lasting" (久; ).
 * Nine is strongly associated with the Chinese dragon, a symbol of magic and power. There are nine forms of the dragon, it is described in terms of nine attributes, and it has nine children. It has 117 scales – 81 yang (masculine, heavenly) and 36 yin (feminine, earthly). All three numbers are multiples of 9 (9 × 13 = 117, 9 × 9 = 81, 9 × 4 = 36) as well as having the same digital root of 9.
 * The dragon often symbolizes the Emperor, and the number nine can be found in many ornaments in the Forbidden City.
 * The circular altar platform (Earthly Mount) of the Temple of Heaven has one circular marble plate in the center, surrounded by a ring of nine plates, then by a ring of 18 plates, and so on, for a total of nine rings, with the outermost having 81 = 9 × 9 plates.
 * The name of the area called Kowloon in Hong Kong literally means: nine dragons.
 * The nine-dotted line delimits certain island claims by China in the South China Sea.
 * The nine-rank system was a civil service nomination system used during certain Chinese dynasties.
 * 9 Points of the Heart (Heal) / Heart Master (Immortality) Channels in Traditional Chinese Medicine.

Ancient Egypt

 * The nine bows is a term used in Ancient Egypt to represent the traditional enemies of Egypt.
 * The Ennead is a group of nine Egyptian deities, who, in some versions of the Osiris myth, judged whether Horus or Set should inherit Egypt.

European culture

 * In Norse mythology, the universe is divided into nine worlds which are all connected by the world tree Yggdrasil.
 * In Norse mythology as well, the number nine is associated with Odin, as that is how many days he hung from the world tree Yggdrasil before attaining knowledge of the runes.

Greek mythology

 * The nine Muses in Greek mythology are Calliope (epic poetry), Clio (history), Erato (erotic poetry), Euterpe (lyric poetry), Melpomene (tragedy), Polyhymnia (song), Terpsichore (dance), Thalia (comedy), and Urania (astronomy).
 * It takes nine days (for an anvil) to fall from heaven to earth, and nine more to fall from earth to Tartarus.
 * Leto labored for nine days and nine nights for Apollo, according to the Homeric Hymn to Delian Apollo.

Mesoamerican mythology

 * The Lords of the Night, is a group of nine deities who each ruled over every ninth night forming a calendrical cycle.

Aztec mythology

 * Mictlan the underworld in Aztec mythology, consists of nine levels.

Mayan mythology

 * The Mayan underworld Xibalba consists of nine levels.
 * El Castillo, the Mayan step-pyramid in Chichén Itzá, consists of nine steps. It is said that this was done to represent the nine levels of Xibalba.

Australian culture
The Pintupi Nine, a group of 9 Aboriginal Australian women who remained unaware of European colonisation of Australia and lived a traditional desert-dwelling life in Australia's Gibson Desert until 1984.

Idioms

 * "to go the whole nine yards-"
 * "A cat-o'-nine-tails suggests perfect punishment and atonement." – Robert Ripley.
 * "A cat has nine lives"
 * "to be on cloud nine"
 * " A stitch in time saves nine"
 * "found true 9 out of 10 times"
 * "possession is nine tenths of the law"
 * The word "K-9" pronounces the same as canine and is used in many US police departments to denote the police dog unit. Despite not sounding like the translation of the word canine in other languages, many police and military units around the world use the same designation.
 * Someone dressed "to the nines" is dressed up as much as they can be.
 * In North American urban culture, "nine" is a slang word for a 9mm pistol or homicide, the latter from the Illinois Criminal Code for homicide.

Technique

 * Stanines, a method of scaling test scores, range from 1 to 9.
 * There are 9 square feet in a square yard.

Literature

 * There are nine circles of Hell in Dante's Divine Comedy.
 * The Nine Bright Shiners, characters in Garth Nix's Old Kingdom trilogy. The Nine Bright Shiners was a 1930s book of poems by Anne Ridler and a 1988 fiction book by Anthea Fraser; the name derives from "a very curious old semi-pagan, semi-Christian" song.
 * The Nine Tailors is a 1934 mystery novel by British writer Dorothy L. Sayers, her ninth featuring sleuth Lord Peter Wimsey.
 * Nine Unknown Men are, in occult legend, the custodians of the sciences of the world since ancient times.
 * In J. R. R. Tolkien's Middle-earth, there are nine rings of power given to men, and consequently, nine ringwraiths. Additionally, The Fellowship of the Ring consists of nine companions.
 * In Lorien Legacies there are nine Garde sent to Earth.
 * Number Nine is a character in Lorien Legacies.
 * In the series A Song of Ice and Fire, there are nine regions of Westeros (the Crownlands, the North, the Riverlands, the Westerlands, the Reach, the Stormlands, the Vale of Arryn, the Iron Islands and Dorne). Additionally, there is a group of nine city-states in western Essos known collectively as the Free Cities (Braavos, Lorath, Lys, Myr, Norvos, Pentos, Qohor, Tyrosh and Volantis).
 * In The Wheel of Time series, Daughter of the Nine Moons is the title given to the heir to the throne of Seanchan, and the Court of the Nine Moons serves as the throne room of the Seanchan rulers themselves. Additionally, the nation of Illian is partially governed by a body known as the Council of Nine, and the flag of Illian displays nine golden bees on it. Furthermore, in the Age of Legends, the Nine Rods of Dominion were nine regional governors who administered individual areas of the world under the ruling world government.

Organizations

 * Divine Nine – The National Pan-Hellenic Council (NPHC) is a collaborative organization of nine historically African American, international Greek-lettered fraternities and sororities.

Places and thoroughfares

 * List of highways numbered 9
 * Ninth Avenue is a major avenue in Manhattan.
 * South Africa has 9 provinces
 * Negeri Sembilan, a Malaysian state located in Peninsular Malaysia, is named as such as it was historically a confederation of nine (sembilan) settlements (nagari) of the Minangkabau migrated from West Sumatra.

Christianity

 * In Christianity there are nine Fruit of the Holy Spirit which followers are expected to have: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control.
 * The Bible recorded that Christ died at the 9th hour of the day (3 pm).

Islam
There are three verses that refer to nine in the Quran.

"We surely gave Moses nine clear signs.1 ˹You, O Prophet, can˺ ask the Children of Israel. When Moses came to them, Pharaoh said to him, “I really think that you, O Moses, are bewitched.”" Note 1: The nine signs of Moses are: the staff, the hand (both mentioned in Surah Ta-Ha 20:17-22), famine, shortage of crops, floods, locusts, lice, frogs, and blood (all mentioned in Surah Al-A'raf 7:130-133). These signs came as proofs for Pharaoh and the Egyptians. Otherwise, Moses had some other signs such as water gushing out of the rock after he hit it with his staff, and splitting the sea.

"Now put your hand through ˹the opening of˺ your collar, it will come out ˹shining˺ white, unblemished.2 ˹These are two˺ of nine signs for Pharaoh and his people. They have truly been a rebellious people.”" Note 2: Moses, who was dark-skinned, was asked to put his hand under his armpit. When he took it out it was shining white, but not out of a skin condition like melanoma.

"And there were in the city nine ˹elite˺ men who spread corruption in the land, never doing what is right."

 * Ramadan, the month of fasting and prayer, is the ninth month of the Islamic calendar.

Other

 * Nine, as the highest single-digit number (in base ten), symbolizes completeness in the Baháʼí Faith. In addition, the word Baháʼ in the Abjad notation has a value of 9, and a 9-pointed star is used to symbolize the religion.
 * The number 9 is revered in Hinduism and considered a complete, perfected and divine number because it represents the end of a cycle in the decimal system, which originated from the Indian subcontinent as early as 3000 BC.
 * In Buddhism, Gautama Buddha was believed to have nine virtues, which he was (1) Accomplished, (2) Perfectly Enlightened, (3) Endowed with knowledge and Conduct or Practice, (4) Well-gone or Well-spoken, (5) the Knower of worlds, (6) the Guide Unsurpassed of men to be tamed, (7) the Teacher of gods and men, (8) Enlightened, and (9) Blessed.
 * Important Buddhist rituals usually involve nine monks.
 * The first nine days of the Hebrew month of Av are collectively known as "The Nine Days" (Tisha HaYamim), and are a period of semi-mourning leading up to Tisha B'Av, the ninth day of Av on which both Temples in Jerusalem were destroyed.
 * Nine is a significant number in Norse Mythology. Odin hung himself on an ash tree for nine days to learn the runes.
 * The Fourth Way Enneagram is one system of knowledge which shows the correspondence between the 9 integers and the circle.
 * Tian's Trigram Number, of Feng Shui, in Taoism.

Astronomy

 * Before 2006 (when Pluto was officially designated as a non-planet), there were nine planets in the Solar System.
 * Messier object M9 is a magnitude 9.0 globular cluster in the constellation Ophiuchus.
 * The New General Catalogue object NGC 9, a spiral galaxy in the constellation Pegasus.

Chemistry

 * The purity of chemicals (see Nine (purity)).
 * Nine is the atomic number of fluorine.

Physiology
A human pregnancy normally lasts nine months, the basis of Naegele's rule.

Psychology
Common terminal digit in psychological pricing.

Sports

 * Nine-ball is the standard professional pocket billiards variant played in the United States.
 * In association football (soccer), the centre-forward/striker traditionally (since at least the fifties) wears the number 9 shirt.
 * In baseball:
 * There are nine players on the field including the pitcher.
 * There are nine innings in a standard game.
 * 9 represents the right fielder's position.
 * NINE: A Journal of Baseball History and Culture, published by the University of Nebraska Press
 * In rugby league, the jersey number assigned to the hooker in most competitions. (An exception is the Super League, which uses static squad numbering.)
 * In rugby union, the number worn by the starting scrum-half.

Technology

 * ISO 9 is the ISO's standard for the transliteration of Cyrillic characters into Latin characters
 * In the Rich Text Format specification, 9 is the language code for the English language. All codes for regional variants of English are congruent to 9 mod 256.
 * The9 Limited (owner of the9.com) is a company in the video-game industry, including former ties to the extremely popular MMORPG World of Warcraft.

Music

 * "Revolution 9", a sound collage which appears on The Beatles' eponymous 1968 album The Beatles (aka The White Album), prominently features a loop of a man's voice repeating the phrase "Number nine".
 * There are 9 semitones in a Major 6th interval in music.
 * There was a superstition among some notable classical music composers that they would die after completing their ninth symphony. Some composers who died after composing their ninth symphony include Ludwig van Beethoven, Anton Bruckner, Antonin Dvorak and Gustav Mahler.
 * Beethoven's Symphony No. 9 is regarded as a masterpiece, and one of the most frequently performed symphonies in the world.
 * A staff of a score contains nine notes who comprise five lines and four spaces.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: 9


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135 film

135 film, more popularly referred to as 35 mm film or 35 mm, is a format of photographic film with a film gauge of 35 mm loaded into a standardized type of magazine (also referred to as a cassette or cartridge) for use in 135 film cameras.

The term 135 was introduced by Kodak in 1934 as a designation for 35 mm film specifically for still photography, perforated with Kodak Standard perforations. It quickly grew in popularity, surpassing 120 film by the late 1960s to become the most popular photographic film size. Despite competition from formats such as 828, 126, 110, and APS, it remains the most popular film size today.

The size of the 135 film frame with its frame's aspect ratio of 1:1.50 has been adopted by many high-end digital single-lens reflex and digital mirrorless cameras, commonly referred to as "full frame". Even though the format is much smaller than historical medium format and large format film, being historically referred to as miniature format or small format, it is much larger than image sensors in most compact cameras and smartphone cameras.

The engineering standard for this film is controlled by ISO 1007 titled '135-size film and magazine'.

35 mm still cameras

The 135 film size is derived from earlier still cameras using lengths of 35 mm movie film, which had the same size but with different perforations. The 35 mm film standard for motion picture film was established in Thomas Edison's lab by William Kennedy Laurie Dickson. Dickson took 70 mm film stock supplied by George Eastman's Eastman Kodak Company. The 70 mm film was cut lengthwise into two equal width (35 mm) strips, spliced together end to end, and then perforated along both edges. The original picture size was 18×24 mm (half the full frame size later used in still photography). There were four perforations on each side of a motion picture frame.

While the Leica camera popularized the format, several 35 mm still cameras used perforated movie film before the Leica was introduced in the 1920s. The first patent for one was issued to Leo, Audobard and Baradat in England in 1908. The first full-scale production camera was the Homéos, a stereo camera, produced by Jules Richard in 1913, and was sold until 1920. It took 18x24 mm stereo pairs, using two Tessar lenses.

In 1909, the French designed a device for small-format photography, the "", which used the 35 mm perforated film to take consecutive hundred views in 18×24 mm. He manufactured, won the gold medal in the Concours Lépine, and in 1910 sold at a small scale and without much success.

The first big-selling 35 mm still camera was the American Tourist Multiple, which also appeared in 1913, at a cost of $175 (at today's prices, the same cost as a modern $3000 Leica.) The first camera to take full-frame 24×36 mm exposures seems to be the Simplex, introduced in the U.S. in 1914. It took either 800 half-frame or 400 full-frame shots on 50 ft (15.2 m) rolls.

The Minigraph, by Levy-Roth of Berlin, another half-frame small camera was sold in Germany in 1915. The patent for the Debrie Sept camera, a combination 35 mm still and movie camera was issued in 1918; the camera sold from 1922.

The Furet camera made and sold in France in 1923 took full-frame 24x36 mm negatives, and was the first cheap small 35 mm camera of similar appearance to more modern models.

Leica

The Leica Camera designed by Oskar Barnack used 35 mm film, and proved that a format as small as 24 mm × 36 mm was suitable for professional photography.

Although Barnack designed his prototype camera around 1913, the first experimental production run of ur-Leicas (Serial No. 100 to 130) did not take place until 1923. Full-scale production of the Leica did not begin until 1925. While by that time there were at least a dozen other 35 mm cameras available, the Leica was a success, and came to be associated with the format. Mostly because of this 35 mm popularity, as well as the entire company legacy, early Leica cameras are considered as highly collectible items. The original Leica prototype holds the record as being the world's most expensive camera, selling for €2.16 million in 2012.

Pre-loaded cassettes and Kodak Retina cameras

In the earliest days, the photographer had to load the film into reusable cassettes and, at least for some cameras, cut the film leader. In 1934, Kodak introduced a 135 daylight-loading single-use cassette. This cassette was engineered so that it could be used in both Leica and Zeiss Ikon Contax cameras along with the camera for which it was invented, namely the Kodak Retina camera. The Retina camera and this daylight loading cassette were the invention of Dr. August Nagel of the Kodak AG Dr. Nagel Werk in Stuttgart. Kodak bought Dr. August Nagel's company in December, 1931, and began marketing the Kodak Retina in the summer of 1934. The first Kodak Retina camera was a Typ 117. The 35 mm Kodak Retina camera line remained in production until 1969. Kodak also introduced a line of American made cameras that were simpler and more economical than the Retina. Argus, too, made a long-lived range of 35 mm cameras; notably the Argus C3. Kodak launched 135-format Kodachrome colour film in 1936. AGFA followed with the introduction of Agfacolor Neu later in the same year.

The designations 235 and 435 refer to 35 mm film in daylight-loading spools, that could be loaded into Contax or Leica style reusable cassettes, respectively, without need of a darkroom. The 335 was a daylight loading spool for the 24 × 23 mm stereo format.

Reflex cameras

Reflex viewfinders, both twin-and single-lens, had been used with earlier cameras using plates and rollfilm.

The first 35 mm single-lens reflex (SLR) was the Kine Exakta, introduced in 1936. World War II interrupted development of the type. After the war, Exakta resumed development and the Contax S model with the now familiar pentaprism viewing feature was introduced in 1949. In the 1950s, the SLR also began to be produced in Japan by such companies as Asahi and Miranda. Asahi's Pentax introduced the instant-return mirror, important for the popularity of SLRs; until then, the viewfinder on an SLR camera blanked as the mirror sprang out of the optical path just before taking the picture, returning when the film was wound on. Nikon's F model, introduced in March 1959, was a system camera that greatly improved the quality and utility of 35 mm format cameras, encouraging professionals (especially photojournalists) to switch from larger format cameras to the versatile, rugged, and fast SLR design. Numerous other film formats waxed and waned in popularity, but by the 1970s, interchangeable-lens SLR cameras and smaller rangefinders, from expensive Leicas to "point-and-shoot" pocket cameras, were all using 35 mm film, and manufacturers had proliferated.

Colour films improved, both for print negatives and reversal slides, while black-and-white films offered smoother grain and faster speeds than previously available. Since 35 mm was preferred by both amateur and professional photographers, makers of film stock have long offered the widest range of different film speeds and types in the format. The DX film-speed encoding system was introduced in the 1980s, as were single-use cameras pre-loaded with 35 mm film and using plastic lenses of reasonable enough quality to produce acceptable snapshots. Automated all-in-one processing and printing machines made 35 mm developing easier and less expensive, so that quality colour prints became available not only from photographic specialty stores, but also from supermarkets, drugstores, and big box retailers, often in less than an hour.

From 1996

In 1996, a smaller format called Advanced Photo System (APS) was introduced by a consortium of photographic companies in an attempt to supersede 135 film. Due in part to its small negative size, APS was not taken seriously as a professional format, despite the production of APS SLRs. In the point-and-shoot markets at which the format was primarily aimed, it enjoyed moderate initial success, but still never rivalled the market penetration of 135. Within five years of its launch, cheap digital compact cameras started becoming widely available, and APS sales plummeted.

While they have shifted the vast majority of their product lines to digital, major camera manufacturers such as Canon and Nikon continued to make expensive professional-grade 35 mm film SLRs until recently (such as the Canon EOS-1V (discontinued in 2018) and the Nikon F6 (discontinued in 2020). Introductory 35 mm SLRs, compact film point-and-shoot cameras, and single-use cameras continue to be built and sold by a number of makers. Leica finally introduced the digital Leica M8 rangefinder in 2007, but continues to make its M series rangefinder film cameras and lenses. A digital camera back for the Leica R9 SLR camera was discontinued in 2007. On March 25, 2009, Leica discontinued the R9 SLR and R-series lenses.

Cassette

Individual rolls of 135 film are enclosed in single-spool, light-tight, metal cassettes to allow cameras to be loaded in daylight. The film is clipped or taped to a spool and exits via a slot lined with flocking. The end of the film is cut on one side to form a leader. It has the same dimensions and perforation pitch as 35 mm movie print film (also called "long pitch", KS-1870, whereas 35 mm professional motion picture camera films are always "short pitch", BH-1866).

Most cameras require the film to be rewound before the camera is opened. Some motorized cameras unwind the film fully upon loading and then expose the images in reverse order, returning the film to the cassette; this protects all exposed frames (except the last one or two), should the camera back be accidentally opened; unexposed film gets spoiled, however. Disposable cameras use the same technique so that the user does not have to rewind.

Since the 1980s, film cassettes have been marked with a DX encoding six-digit barcode pattern, which identifies the manufacturer and film type (and thus processing method), and the number of exposures, for the use of photofinishing laboratories. The cassettes are also manufactured with a Camera Auto Sensing code constructed as two rows of six rectangular areas on the metal cassette surface which are either conductive or insulating, representing 32 possible film speeds, eight possible film lengths, and four possible values of exposure tolerance or latitude. Conforming cameras detect at least some of these areas; only three contacts are needed to set a light meter for the four most popular film speeds.

Film type and speed
The 135 film has been made in several emulsion types and sensitivities (film speeds) described by ISO standards. Since the introduction of digital cameras the most usual films have colour emulsions of ISO 100/21° to ISO 800/30°. Films of lower sensitivity (and better picture quality) and higher sensitivity (for low light) are for more specialist purposes. There are colour and monochrome films, negative and positive. Monochrome film is usually panchromatic; orthochromatic has fallen out of use. Film designed to be sensitive to infrared radiation can be obtained, both monochrome and with false-colour (or pseudocolour) rendition. More exotic emulsions have been available in 135 than other roll-film sizes.

Image format

The term 135 format usually refers to a 24×36 mm film format, commonly known as 35 mm format. The 24×36 mm format is common to higher-end digital image sensors, where it is typically referred to as full-frame format.

On 135 film, the typical cameras produce a frame where the longer dimension of the 24×36 mm frame runs parallel to the length of the film. The perforation size and pitch are according to the standard specification KS-1870. For each frame, the film advances 8 perforations. This is specified as 38.00 mm. This allows for 2 mm gaps between frames. Camera models typically have different locations for the sprocket which advances the film. Therefore, each camera model's frame may vary in position relative to the perforations. The film is approximately 0.14 mm thick.

Other image formats have been applied to 135 film, such as the half-frame format of 18×24 mm which earned some popularity in the 1960s, and the 24×24 mm of the Robot cameras. The successful range of Olympus Pen F cameras utilized the smaller half-frame size, allowing the design of a very compact SLR camera. Unusual formats include the 24×32 mm and 24×34 mm on the early Nikon rangefinders, and 24×23 mm for use with some stereo cameras. In 1967, the Soviet KMZ factory introduced a 24×58 mm panoramic format with its Horizont camera (descendants of which are called, in the Roman alphabet, Horizon). In 1998, Hasselblad and Fuji introduced a 24×65 mm panoramic format with their XPan/TX-1 camera. There is also a 21×14 mm format used by Tessina subminiature camera.

Length

The film is available in lengths for varying numbers of exposures. The standard full-length roll has always been 36 exposures (assuming a standard 24×36 frame size). Through about 1980, 20 exposure rolls were the only shorter length with widespread availability. Since then, 20 exposure rolls have been largely discontinued in favour of 24- and 12-exposure rolls. The length of film provided includes the length required for the indicated number of exposures plus sufficient additional length for the film spoiled by being exposed to ambient light when it is drawn out of the canister, across the back of the camera, and securely engaged with the film advancing spool, before the camera back is closed. A camera that uses less than the maximum distance between the spools may be able to make one additional exposure. Self-loading cameras that load the film after being closed don't spoil the additional length provided for conventional loading and can make that additional length available for two or three additional exposures. The same length can be available for exposures in any camera if it is loaded without exposing the film to light, e.g. in a darkroom or a dark bag. A 27-exposure disposable camera uses a standard 24-exposure cassette loaded in the dark.

Other, mostly shorter, lengths have been manufactured. There have been some 6-, 8-, 10-, and 15-exposure rolls given away as samples, sometimes in disposable cameras, or used by insurance adjusters to document damage claims. Twelve-exposure rolls have been used widely in the daily press. Photographers who load their own cassettes can use any length of film – with thinner film base up to 45 exposures will fit.

The Ilford HP black-and-white film, on a thin polyester base, allowed 72 exposures in a single cassette. They produced special reels and tanks to allow this to be processed.

Use in digital cameras

Digital sensors are available in various sizes. Professional DSLR cameras usually use digital image sensors which approximate the dimensions of the 35 mm format, sometimes differing by fractions of a millimetre on one or both dimensions. Since 2007, Nikon has referred to their 35 mm format by the trade mark FX. Other makers of 35 mm format digital cameras, including Leica, Sony, and Canon, refer to their 35 mm sensors simply as full frame.

Most consumer DSLR cameras use smaller sensors, with the most popular size being APS-C which measures around 23×15 mm (giving it a crop factor of 1.5–1.6). Compact cameras have smaller sensors with a crop factor of around 3 to 6.

Use in smart phones
Most smartphones (as of 2024) have a default aspect ratio of 4:3 (crop factor of 1.33). Mimicking 35mm film in a smartphone requires cropping to a 3:2 aspect ratio (crop factor of 1.5-1.6). For an authentic homage, one can apply creative digital filters like the ones commonly used in Instagram that map the colour profile to a characteristic look. Different brands of 35mm film would achieve the creative colour profile through a chemical process. For example Fuji Velvia film gave the photo a characteristic of saturated colours under daylight, high contrast, and exceptional sharpness.

In recent years, the phone app "Dazzcam" has gained popularity for its resemblance to 35mm film cameras.

Lenses
A true normal lens for 35 mm format would have a focal length of 43 mm, the diagonal measurement of the format. However, lenses of 43 mm to 60 mm are commonly considered normal lenses for the format, in mass production and popular use. Common focal lengths of lenses made for the format include 24, 28, 35, 50, 85, 105, and 135 mm. Most commonly, a 50 mm lens is the one considered normal; any lens shorter than this is considered a wide angle lens and anything above is considered a telephoto lens. Even then, wide angles shorter than 24 mm is called an extreme wide angle. Lenses above 50 mm but up to about 100 mm are called short telephoto or sometimes, as portrait telephotos, from 100 mm to about 200 mm are called medium telephotos, and above 300 mm are called long telephotos.

With many smaller formats now common (such as APS-C), lenses are often advertised or marked with their "35 mm equivalent" or "full-frame equivalent" focal length as a mnemonic, due to the historic prevalence of the 35 mm format. This 'equivalent' is computed by multiplying (a) the true focal length of the lens by (b) the ratio of the diagonal measurement of the native format to that of the 35 mm format.

As a result, a lens for an APS-C (18×24 mm) format camera body with a focal length of 40 mm, might be described as "60 mm (35 mm equivalent)". Although its true focal length remains 40 mm, its angle of view is equivalent to that of a 60 mm lens on a 35 mm format (24×36 mm) camera. Another example is the lens of the 2/3 inch format Fujifilm X10, which is marked with its true zoom range "7.1–28.4 mm" but has a 35 mm-equivalent zoom range of "28–112 mm".

title: 135 film


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120 film

120 is a film format for still photography introduced by Kodak for their Brownie No. 2 in 1901. It was originally intended for amateur photography but was later superseded in this role by 135 film. 120 film survives to this day as the only medium format film that is readily available to both professionals and amateur enthusiasts.

Characteristics
The 120 film format is a roll film which is nominally between 60.7 mm and 61.7 mm wide. Most modern films made today are roughly 61 mm (2.4 inches) wide. The film is held in an open spool originally made of wood with metal flanges, later with all-metal, and finally with all-plastic. The length of the film is nominally between 820 mm and 850 mm, according to the ISO 732:2000 standard. However, some films may be as short as 760 mm. The film is attached to a piece of backing paper longer and slightly wider than the film. The backing paper protects the film while it is wound on the spool, with enough extra length to allow loading and unloading the roll in daylight without exposing any of the film. Frame number markings for three standard image formats (6×4.5, 6×6, and 6×9 [4:3, 1:1, and 2:3 aspect ratios]; see below) are printed on the backing paper.

The 220 format was introduced in 1965 and is the same width as 120 film, but with about double the length of film and thus twice the number of possible exposures per roll. Unlike 120 film, however, there is no backing paper behind the film itself, just a leader and a trailer. This results in a longer film on the same spool, but there are no printed frame numbers. Because of this, 220 film cannot be used in cameras that rely on reading frame numbers through a red window. Also, since the film alone is thinner than a film with a backing paper, a special pressure plate may be required to achieve optimal focus if the film is registered against its back side. Some cameras capable of using both 120 and 220 film will have a two position adjustment of the pressure plate (e.g. the Pentax 6x7, Mamiya C220 or Mamiya C330) while others will require different film backs e.g. the Pentax 645 or Kowa Six.

The specifications for 120 and 220 film are defined in the ISO 732 standard. Earlier editions of ISO 732 also provided international standards for the 127 and 620 film formats.

Frame sizes
120 film allows several frame sizes.

† User selectable on newer cameras, if a roll is only partially used then a "kink" may appear in the film where the roll touches rollers in a film back magazine and this may end up on a frame; this is not a problem when 15 exposures are used as the gaps between exposed frames is larger, nor if the camera is not used intermittently.

The 6×9 frame has the same aspect ratio as the standard 24×36 mm frame of 135 film. The 6×7 frame enlarges almost exactly to 8×10 inch paper, for which reason its proponents call it "ideal format". 6×4.5 is the smallest and least expensive roll-film frame size.

The wide 6×12, 6×17, and 6×24 cm frames are produced by special-purpose panoramic cameras. Most of these cameras use lenses intended for large format cameras for simplicity of construction.

Cameras using 120 film will often combine the numbers of the frame size in the name e.g. Pentax 6×7 (6×7), Fuji 617 (6×17), and many 645s (6×4.5). The number '6' in general, and the word 'six' are also commonly used in naming cameras e.g. Kiev 60 and Pentacon Six.

Other similar 6 cm roll films
The 105 format was introduced by Kodak in 1898 for their first folding camera and was the original 6×9 cm format roll film. The 117 format was introduced by Kodak in 1900 for their first Brownie camera, the No.1 Brownie, 6×6 cm format. These formats used the same width film as 120 film, but with slightly different spools. The 105 spool has a much wider flange, similar to the 116 spool, while the 117 spool's flange is slightly narrower than the 120. The 105 and 620 spools also have much thinner flanges than the 117 and 120 spools (0.635 mm vs. 1.524 mm); as a result, an unmodified 120 spool will not fit a camera designed for 105 film, such as a No. 1 Folding Pocket Kodak, as the overall length between the outside of the flanges is too long to fit the width of the film chamber.

The 620 format was introduced by Kodak in 1931 as an intended alternative to 120. Although mostly used by Kodak cameras, it became very popular. The 620 format is essentially the same film on a thinner and narrower all-metal spool (the 120 spool core was made of wood at that time):

 * 105 2.509" (63.7 mm) width, 1.250" (31.8 mm) flange, 0.468" (11.9 mm) core
 * 117 2.470" (62.7 mm) width, 0.875" (22.2 mm) flange, 0.468" (11.9 mm) core
 * 120 2.???" width, 0.990" (25.1 mm) flange, 0.468" (11.9 mm) core
 * 620 2.???" width, 0.905" (23.0 mm) flange, 0.280" (7.1 mm) core

Hence the 620 is sometimes referred to as "small hole" 6×6 or 6×9 as opposed to 120 "large hole". The 620 format was discontinued by Kodak in 1995, but it is possible to rewind 120 film onto a 620 spool in the darkroom for use in 620 cameras. According to Kodak, the narrower metal spool allowed building smaller cameras. Nonetheless the 120 format cast-metal bodied Voigtländer Perkeo remains smaller than any 620 format camera.

title: 120 film


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Cessna 172

The Cessna 172 Skyhawk is an American four-seat, single-engine, high wing, fixed-wing aircraft made by the Cessna Aircraft Company. First flown in 1955, more 172s have been built than any other aircraft. It was developed from the 1948 Cessna 170 but with tricycle landing gear rather than conventional landing gear. The Skyhawk name was originally used for a trim package, but was later applied to all standard-production 172 aircraft, while some upgraded versions were marketed as the Cutlass, Powermatic, and Hawk XP. The aircraft was also produced under license in France by Reims Aviation, which marketed upgraded versions as the Reims Rocket.

Measured by its longevity and popularity, the Cessna 172 is the most successful aircraft in history. Cessna delivered the first production model in 1956, and, the company and its partners had built more than 44,000 units. With a break from 1986–96, the aircraft remains in production today.

A light general aviation airplane, the Skyhawk's main competitors throughout its lifetime have been the Beechcraft Musketeer and Grumman American AA-5 series (neither currently in production), the Piper PA-28 Cherokee, and, more recently, the Diamond DA40 Star and Cirrus SR20.

Design and development
The Cessna 172 started as a tricycle landing gear variant of the taildragger Cessna 170, with a basic level of standard equipment. In January 1955, Cessna flew an improved variant of the Cessna 170, a Continental O-300-A-powered Cessna 170C with larger elevators and a more angular tailfin. Although the variant was tested and certified, Cessna decided to modify it with a tricycle landing gear, and the modified Cessna 170C flew again on June 12, 1955. To reduce the time and cost of certification, the type was added to the Cessna 170 type certificate as the Model 172. Later, the 172 was given its own type certificate. The 172 became an overnight sales success, and over 1,400 were built in 1956, its first full year of production.

Early 172s were similar in appearance to the 170s, with the same straight aft fuselage and tall landing gear legs, although the 172 had a straight tailfin while the 170 had a rounded fin and rudder. In 1960, the 172A incorporated revised landing gear and the swept-back tailfin, which is still in use today.

The final aesthetic development, found in the 1963 172D and all later 172 models, was a lowered rear deck allowing an aft window. Cessna advertised this added rear visibility as "Omni-Vision".

Production halted in the mid-1980s, but resumed in 1996 with the 160 hp (120 kW) Cessna 172R Skyhawk. Cessna supplemented this in 1998 with the 180 hp (135 kW) Cessna 172S Skyhawk SP.

Modifications
The Cessna 172 may be modified via a wide array of supplemental type certificates (STCs), including increased engine power and higher gross weights. Available STC engine modifications increase power from 180 to 210 hp, add constant-speed propellers, or allow the use of automobile gasoline. Other modifications include additional fuel tank capacity in the wing tips, added baggage compartment tanks, added wheel pants to reduce drag, or enhanced landing and takeoff performance and safety with a STOL kit. The 172 has also been equipped with the 180 hp fuel injected Superior Air Parts Vantage engine.

World records
From December 4, 1958, to February 7, 1959, Robert Timm and John Cook set the world record for (refueled) flight endurance in a used Cessna 172, registration number N9172B. They took off from McCarran Field (now Harry Reid International Airport) in Las Vegas, Nevada, and landed back at McCarran Field after 64 days, 22 hours, 19 minutes and 5 seconds in a flight covering an estimated 150,000 miles, over 6 times further than flying around the world at the equator. The flight was part of a fund-raising effort for the Damon Runyon Cancer Fund. The aircraft is now on display at the airport.

Variants
Cessna has historically used model years similar to U.S. auto manufacturers, with sales of new models typically starting a few months prior to the actual calendar year. Introduced in November 1955 for the 1956 model year as a development of the Cessna 170B with tricycle landing gear, dubbed "Land-O-Matic" by Cessna. The 172 also featured a redesigned tail similar to the experimental 170C, "Para-Lift" flaps, and a maximum gross weight of 2200 lb while retaining the 170B's 145 hp Continental O-300-A six-cylinder, air-cooled engine. The 1957 and 1959 model years brought only minor changes, while 1959 introduced a new cowling for improved engine cooling. The prototype 172, c/n 612, was modified from 170 c/n 27053, which previously served as the prototype of the 170B. A total of 3,757 were constructed over the four model years; 1,178 (1956), 1,041 (1957), 750 (1958), 788 (1959).

1960 model year with a swept-back vertical tail and rudder and powered by a 145 hp O-300-C engine. It was also the first 172 to be certified for floatplane operation. 994 built.

1961 model year with shorter landing gear, engine mounts lengthened by three inches (76 mm), a reshaped cowling, a pointed propeller spinner, and an increased gross weight of 2250 lb. For the first time, the Skyhawk name was applied to an available deluxe option package that included optional wheel fairings, avionics, and a cargo door along with full exterior paint rather than partial paint stripes. The Skyhawk was also powered by an O-300-D in place of the O-300-C of the standard model. 989 built.

1962 model year with fiberglass wingtips, redesigned wheel fairings, a key starter to replace the previous pull-starter, and an optional autopilot. The seats were redesigned to be six-way adjustable, and a child seat was made optional to allow two children to be carried in the baggage area. 810 built.

1963 model year with a cut down rear fuselage with a wraparound Omni-Vision rear window, a one-piece windshield, increased horizontal stabilizer span, and a folding hat shelf in the rear cabin. Gross weight was increased to 2300 lb, where it would stay until the 172P. New rudder and brake pedals were also added. 1,011 were built by Cessna, while a further 18 were produced by Reims Aviation in France as the F172D.

1964 model year with a redesigned instrument panel with center-mounted avionics and circuit breakers replacing the electrical fuses of previous models. 1,209 built, 67 built by Reims as the F172E.

1965 model year with electrically-operated flaps to replace the previous lever-operated system and improved instrument lighting. 1,400 built, plus 94 by Reims as the F172F.

The 172F formed the basis for the U.S. Air Force's T-41A Mescalero primary trainer, which was used during the 1960s and early 1970s as initial flight screening aircraft in USAF Undergraduate Pilot Training (UPT). Following their removal from the UPT program, some extant USAF T-41s were assigned to the U.S. Air Force Academy for the cadet pilot indoctrination program, while others were distributed to Air Force aero clubs.

1966 model year with a longer, more pointed spinner and sold for US$12,450 in its basic 172 version and US$13,300 in the upgraded Skyhawk version. 1,474 built (including 26 as the T-41A), plus 140 by Reims as the F172G.

1967 model year with a 60A alternator replacing the generator, a rotating beacon replacing the flashing unit, redesigned wheel fairings, and a shorter-stroke nose gear oleo to reduce drag and improve the appearance of the aircraft in flight. A new cowling was used, introducing shock-mounts that transmitted lower noise levels to the cockpit and reduced cowl cracking. The electric stall warning horn was replaced by a pneumatic one. 1,586 built (including 34 as the T-41A), plus 435 by Reims as the F172H for both the 1967 and 1968 model years.

The 1968 model year marked the beginning of the Lycoming-powered 172s, with the 172I introduced with a Lycoming O-320-E2D engine of 150 hp, an increase of 5 hp over the Continental powerplant. The increased power resulted in an increase in optimal cruise from 130 mi/h true airspeed (TAS) to 131 mi/h TAS. There was no change in the sea level rate of climb at 645 ft per minute. Starting with this model, the standard and deluxe Skyhawk models were no longer powered by different engines. The 172I also introduced the first standard "T" instrument arrangement. 649 built.

For 1968, Cessna planned to replace the 172 with a newly designed aircraft called the 172J, featuring the same general configuration but with a more sloping windshield, a strutless cantilever wing, a more stylish interior, and various other improvements. A single 172J prototype, registered N3765C (c/n 660), was built. However, the popularity of the previous 172 with Cessna dealers and flight schools prompted the cancellation of the replacement plan, and the 172J was redesignated as the 177 from the second prototype onward and sold alongside the 172.

Introduced for the 1969 model year with a redesigned tailfin cap and reshaped rear windows enlarged by 16 in2. Optional long-range 52 USgal wing fuel tanks were also offered. The 1970 model year featured fiberglass, downward-shaped, conical camber wingtips and optional fully articulated seats. 2,055 built for both model years, plus 50 by Reims as the F172K.

Introduced for the 1971 model year with tapered, tubular steel landing gear legs replacing the original flat spring steel legs, increasing landing gear width by 12 in. The new landing gear was lighter, but required aerodynamic fairings to maintain the same speed and climb performance as experienced with the flat steel design. 172L also had a nose-mounted landing light, a bonded baggage door, and optional cabin skylights. The 1972 model year introduced a plastic fairing between the dorsal fin and vertical fin to introduce a greater family resemblance to the 182's vertical fin. 1972 also introduced a reduced-diameter propeller, bonded cabin doors, and improved instrument panel controls. 1,535 built for both model years, plus 100 by Reims as the F172L.

Introduced for the 1973 model year with a "Camber-Lift" wing with a drooped leading edge for improved low-speed handling, a key-locking baggage door, and new lighting switches. The 1974 model year introduced the Skyhawk II, which was sold alongside the baseline 172M and Skyhawk models with higher standard equipment, including a second nav/comm radio, an ADF and transponder, a larger baggage compartment, and nose-mounted dual landing lights. 1975 introduced inertia-reel shoulder harnesses and an improved instrument panel and door seals. Beginning in 1976, Cessna stopped marketing the aircraft as the 172 and began exclusively using the "Skyhawk" designation. This model year also saw a redesigned instrument panel to hold more avionics. Among other changes, the fuel and other small gauges were relocated to the left side for improved pilot readability compared with the earlier 172 panel designs. 6,826 built; 4,926 (1973–75) and 1,900 (1976), plus 610 by Reims as the F172M.

1977 model year powered by a 160 hp Lycoming O-320-H2AD engine designed to run on 100-octane fuel (hence the "Skyhawk/100" name), whereas all previous engines used 80/87 fuel. Other changes included pre-select flap control and optional rudder trim. The 1978 model year brought a 28-volt electrical system to replace the previous 14-volt system as well as optional air conditioning. The 1979 model year increased the flap-extension speed to 110 kn. 6,425 total built; 1,725 (1977), 1,725 (1978), 1,850 (1979), and 1,125 (1980), plus 525 by Reims as the F172N.

There was no "O" model 172, to avoid confusion with the number zero.

Introduced for the 1981 model year with a Lycoming O-320-D2J engine replacing the O-320-H2AD of the 172N, which had proven unreliable. Other changes included a decreased maximum flap deflection from 40 degrees to 30 to allow a gross weight increase from 2300 lb to 2400 lb. A 62 gal wet wing and air conditioning were optional. The 1982 model year moved the landing lights from the nose to the wing to increase bulb life, while 1983 added some minor soundproofing improvements and thicker windows. 1984 introduced a second door latch pin, a thicker windshield and side windows, additional avionics capacity, and low-vacuum warning lights. 2,664 total built; 1,052 (1981), 724 (1982), 319 (1983), 179 (1984), 256 (1985), and 134 (1986), plus 215 by Reims as the F172P. Following the end of 172P production in 1986, Cessna ceased production of the Skyhawk for ten years.

Introduced for the 1983 model year, the 172Q was given the name "Cutlass" to create an affiliation with the 172RG Cutlass RG, although it was actually a 172P with a Lycoming O-360-A4N engine of 180 hp. The aircraft had a gross weight of 2550 lb and an optimal cruise speed of 122 kn compared to the 172P's cruise speed of 120 kn on 20 hp less. It had a useful load that was about 100 lb more than the Skyhawk P and a rate of climb that was actually 20 ft per minute lower, due to the higher gross weight. The Cutlass II was offered as a deluxe model of the 172Q, as was the Cutlass II/Nav-Pac with IFR equipment. The 172Q was produced alongside the 172P for the 1983 and 1984 model years before being discontinued. Sources disagree on the exact number of 172Q aircraft built, and the construction numbers listed on the Federal Aviation Administration type certificate overlap with those of the 1983 and 1984 172P.

The Skyhawk R was introduced in 1996 and is powered by a derated Lycoming IO-360-L2A producing a maximum of 160 horsepower (120 kW) at just 2,400 rpm. This is the first Cessna 172 to have a factory-fitted fuel-injected engine.

The 172R's maximum takeoff weight is 2450 lb. This model year introduced many improvements, including a new interior with soundproofing, an all new multi-level ventilation system, a standard four point intercom, contoured, energy absorbing, 26g front seats with vertical and reclining adjustments and inertia reel harnesses.

The Cessna 172S was introduced in 1998 and is powered by a Lycoming IO-360-L2A producing 180 hp. The maximum engine rpm was increased from 2,400 rpm to 2,700 rpm resulting in a 20 hp increase over the "R" model. As a result, the maximum takeoff weight was increased to 2550 lb. This model is marketed under the name Skyhawk SP, although the Type Certification data sheet specifies it is a 172S.

The 172S is built primarily for the private owner-operator and is, in its later years, offered with the Garmin G1000 avionics package and leather seats as standard equipment.

, the 172S model was the only Skyhawk model in production.

Variants under 175 type certificate
As the Cessna 175 Skylark had gained a reputation for poor engine reliability, Cessna attempted to regain sales by rebranding the aircraft as a variant of the 172.

The 175 Skylark was rebranded for the 1963 model year as the P172D Powermatic, continuing where the Skylark left off at 175C. It was powered by a 175 hp Continental GO-300-E with a geared reduction drive powering a constant-speed propeller, increasing cruise speed by 11 mi/h over the standard 172D. It differed from the 175C in that it had a cut-down rear fuselage with an "Omni-Vision" rear window and an increased horizontal stabilizer span. A deluxe version was marketed as the Skyhawk Powermatic with a slightly increased top speed. Despite the rebranding, sales did not meet expectations, and the 175 type was discontinued for the civilian market after the 1963 model year. 65 were built, plus 3 by Reims as the FP172D.

Although the 175 type was discontinued for the civilian market, Cessna continued to produce the aircraft for the United States Armed Forces as the T-41 Mescalero. Introduced in 1967, the R172E was built in T-41B, T-41C, and T-41D variants for the US Army, USAF Academy, and US Military Aid Program, respectively. As the T-41B, the R172E was powered by a fuel-injected 210 hp Continental IO-360-D or -DE driving a constant-speed propeller, and featured a 28V electrical system, jettisonable doors, an openable right front window, a 6.00x6 nose wheel tire and military avionics, but no baggage door. The T-41C was similar to the T-41B, but had a 14V electrical system, a fixed-pitch propeller, civilian avionics, and no rear seats. The T-41D featured a 28V electrical system, four seats, corrosion-proofing, reinforced flaps and ailerons, a baggage door, and provisions for wing-mounted pylons. 255 (T-41B), 45 (T-41C), and 34 (T-41D) built. While Cessna produced the R172E exclusively for military use, Reims built a civilian model as the FR172E Reims Rocket, with 60 built for the 1968 model year.

The R172F was similar to the R172E and was built in both T-41C and T-41D variants. 7 (T-41C) and 74 (T-41D) built, plus 85 by Reims as the FR172F Reims Rocket for the 1969 model year.

The R172G was similar to the R172E/F, differing in that it was certified to be powered by a 210 hp Continental IO-360-C, -D, -CB, or -DB engine. 28 (T-41D) built, plus 80 by Reims as the FR172G Reims Rocket for the 1970 model year.

The R172H introduced the extended dorsal fillet of the 172L to the T-41D. It was also certified to be powered by a 210 hp Continental IO-360-C, -D, -H, -CB, -DB, or -HB engine. 163 (T-41D) built, plus 125 by Reims as the FR172H Reims Rocket for the 1971 and 1972 model years.

Certified to be powered by a 210 hp Continental IO-360-H or -HB engine. Only one was built by Cessna, while Reims built 240 as the FR172J Reims Rocket for the 1973 through 1976 model years.

Following the success of the Reims Rocket in Europe, Cessna decided to once again produce the 175 type for the civilian market as the R172K Hawk XP, beginning with the 1977 model year. It was powered by a derated 195 hp Continental IO-360-K or -KB engine driving a McCauley constant-speed propeller and featured a new cowling with landing lights and an upgraded interior. The Hawk XP II was also available with full IFR avionics. However, owners claimed that the increased performance of the "XP" did not compensate for its increased purchase price and the higher operating costs associated with the larger engine. The aircraft was well accepted for use on floats, however, as the standard 172 is not a strong floatplane, even with only two people on board, while the XP's extra power improves water takeoff performance dramatically. 1 (1973 prototype), 725 (1977), 205 (1978), 270 (1979), 200 (1980), and 55 (1981) built, plus 85 (30 in 1977, 55 in 1978–81) by Reims as the FR172K Reims Rocket for the 1977 through 1981 model years.

Cessna introduced a retractable landing gear version of the 172 in 1980, designating it as the 172RG and marketing it as the Cutlass RG.

The Cutlass RG sold for about US$19,000 more than the standard 172 and featured a variable-pitch, constant-speed propeller and a more powerful Lycoming O-360-F1A6 engine of 180 hp, giving it an optimal cruise speed of 140 knots (260 km/h), compared to 122 kn for the contemporary 160 hp 172N or 172P. It also had more fuel capacity than a standard Skyhawk, 62 gal versus 53 gal, giving it greater range and endurance.

The 172RG first flew on August 24, 1976. It was the lowest-priced four-seat retractable-gear airplane on the U.S. market when it was introduced. Although the general aviation aircraft market was contracting at the time, the RG proved popular as an inexpensive flight-school trainer for complex aircraft and commercial pilot ratings under U.S. pilot certification rules, which required demonstrating proficiency in an aircraft with retractable landing gear.

The 172RG uses the same basic landing gear as the heavier R182 Skylane RG, which Cessna touted as a benefit, saying it was a proven design; however, owners have found the landing gear to have higher maintenance requirements than comparable systems from other manufacturers, with several parts prone to rapid wear or cracking. Compared to a standard 172, the 172RG is easier to load with its center of gravity too far aft, which adversely affects the aircraft's longitudinal stability.

While numbered and marketed as a 172, the 172RG was certified on the Cessna 175 type certificate. No significant design updates were made to the 172RG during its five-year model run. 1,191 were produced.

Although it is slower and has less passenger and cargo capacity than popular competing single-engine retractable-gear aircraft such as the Beechcraft Bonanza, the Cutlass RG is praised by owners for its relatively low operating costs, robust and reliable engine, and docile flying qualities comparable to the standard 172, although it has higher landing gear maintenance and insurance costs than a fixed-gear 172.

In April 2018, the U.S. Federal Aviation Administration (FAA) repealed the requirement for complex aircraft or commercial pilot candidates to demonstrate proficiency in an aircraft with retractable landing gear; this change was a reaction to increasing maintenance costs of older retractable-gear trainers commonly used for these ratings.

Special versions
Model introduced in July 2014 for 2015 customer deliveries, powered by a 155 hp Continental CD-155 diesel engine installed by the factory under a supplemental type certificate. Initial retail price in 2014 was $435,000 (~$ in ). The model has a top speed of 131 kn and burns 3 u.s.gal per hour less fuel than the standard 172. As a result, the model has an 885 nmi range, an increase of more than 38% over the standard 172. This model is a development of the proposed and then cancelled Skyhawk TD. Cessna has indicated that the JT-A will be made available in 2016.
 * J172T

In reviewing this new model Paul Bertorelli of AVweb said: "I'm sure Cessna will find some sales for the Skyhawk JT-A, but at $420,000, it's hard to see how it will ignite much market expansion just because it's a Cessna. It gives away $170,000 to the near-new Redbird Redhawk conversion which is a lot of change to pay merely for the smell of a new airplane. Diesel engines cost more than twice as much to manufacture as gasoline engines do and although their fuel efficiency gains back some of that investment, if the complete aircraft package is too pricey, the debt service will eat up any savings, making a new aircraft not just unattractive, but unaffordable. I haven't run the numbers on the JT-A yet, but I can tell from previous analysis that there are definite limits."

The model was certified by both EASA and the FAA in June 2017. It was discontinued in May 2018, due to poor sales as a result of the aircraft's high price, which was twice the price of the same aircraft as a diesel conversion. The aircraft remains available as an STC conversion from Continental Motors, Inc.

In July 2010, Cessna announced it was developing an electrically powered 172 as a proof-of-concept in partnership with Bye Energy. In July 2011, Bye Energy, whose name had been changed to Beyond Aviation, announced the prototype had commenced taxi tests on 22 July 2011 and a first flight would follow soon. In 2012, the prototype, using Panacis batteries, engaged in multiple successful test flights. The R&D project was not pursued for production.

Canceled model
On October 4, 2007, Cessna announced its plan to build a diesel-powered model, to be designated the 172 Skyhawk TD ("Turbo Diesel") starting in mid-2008. The planned engine was to be a Thielert Centurion 2.0, liquid-cooled, two-liter displacement, dual overhead cam, four-cylinder, in-line, turbo-diesel with full authority digital engine control with an output of 155 hp and burning Jet-A fuel. In July 2013, the 172TD model was canceled due to Thielert's bankruptcy. The aircraft was later refined into the Turbo Skyhawk JT-A, which was certified in June 2014 and discontinued in May 2018.

Simulator company Redbird Flight uses the same engine and reconditioned 172 airframes to produce a similar model, the Redbird Redhawk.

Premier Aircraft Sales also announced in February 2014 that it would offer refurbished 172 airframes equipped with the Continental/Thielert Centurion 2.0 diesel engine.

Military operators
A variant of the 172, the T-41 Mescalero was used as a trainer with the United States Air Force and Army. In addition, the United States Border Patrol uses a fleet of 172s for aerial surveillance along the Mexico-US border.

From 1972 to 2019 the Irish Air Corps used the Reims version for aerial surveillance and monitoring of cash, prisoner and explosive escorts, in addition to army cooperation and pilot training roles.

For T-41 operators, see Cessna T-41 Mescalero.

 * 🇦🇴 Angola
 * FAPA/DAA
 * Austrian Air Force 1× 172
 * Bolivian Air Force 3× 172K
 * Chilean Army 18× R172K (retired)
 * Colombian Air Force – To replace Cessna T-41s used for primary training with deliveries from June 2021.
 * Ecuadorian Air Force 8× 172F
 * Ecuadorian Army 1× 172G
 * Guatemalan Air Force 6× 172K
 * Honduran Air Force 3
 * Indonesian Air Force
 * Ecuadorian Air Force 8× 172F
 * Ecuadorian Army 1× 172G
 * Guatemalan Air Force 6× 172K
 * Honduran Air Force 3
 * Indonesian Air Force
 * Honduran Air Force 3
 * Indonesian Air Force
 * Indonesian Air Force

 * Iraqi Air Force
 * Irish Air Corps 8× FR172H, 1× FR172K Five FR172H remained in service until 2019.
 * Air Reconnaissance Unit 2
 * 🇱🇹 Lithuania
 * Lithuanian Air Force 1
 * Malagasy Air Force 4× 172M
 * Nicaraguan Air Force 7
 * Pakistan Air Force 4× 172N
 * Philippine Navy 1×172F, 1×172N, 4x172S
 * Royal Saudi Air Force 8× F172G, 4× F172H, 4× F172M
 * Republic of Singapore Air Force 8× 172K, delivered 1969 and retired 1972.
 * Suriname Air Force (One in service for sale)
 * Pakistan Air Force 4× 172N
 * Philippine Navy 1×172F, 1×172N, 4x172S
 * Royal Saudi Air Force 8× F172G, 4× F172H, 4× F172M
 * Republic of Singapore Air Force 8× 172K, delivered 1969 and retired 1972.
 * Suriname Air Force (One in service for sale)
 * Republic of Singapore Air Force 8× 172K, delivered 1969 and retired 1972.
 * Suriname Air Force (One in service for sale)
 * Suriname Air Force (One in service for sale)
 * Suriname Air Force (One in service for sale)

Accidents and incidents

 * On February 13, 1964, Ken Hubbs, second baseman for the Chicago Cubs and winner of the Rookie of the Year Award and the Gold Glove Award, was killed when the Cessna 172 he was flying crashed near Bird Island in Utah Lake.
 * On October 23, 1964, David Box, lead singer for The Crickets on their 1960 release version of "Peggy Sue Got Married" and "Don't Cha Know" and later a solo artist, was killed when the Cessna 172 he was aboard crashed in northwest Harris County, Texas, while en route to a performance. Box was the second lead vocalist for The Crickets to die in a plane crash, following Buddy Holly.
 * On August 31, 1969, American professional boxer Rocky Marciano was killed when the Cessna 172 in which he was a passenger crashed on approach to an airfield outside Newton, Iowa.
 * On September 25, 1978, a Cessna 172, N7711G, and Pacific Southwest Airlines Flight 182, a Boeing 727, collided over San Diego, California. There were 144 fatalities, two in the Cessna 172, 135 on the PSA Flight 182 and seven on the ground.
 * On May 28, 1987, a rented Reims Cessna F172P, registered D-ECJB, was used by German teenage pilot Mathias Rust in an unauthorized flight from Helsinki-Malmi Airport through Soviet airspace to land near the Red Square in Moscow, all without being intercepted by Soviet air defense.
 * On April 9, 1990, Atlantic Southeast Airlines Flight 2254, an Embraer EMB 120 Brasilia, collided head-on with a Civil Air Patrol Cessna 172, N99501, while en route from Gadsden Municipal Airport to Hartsfield–Jackson Atlanta International Airport. The Cessna crashed, killing two occupants, but the Brasilia made a safe emergency landing.
 * On January 5, 2002, high school student Charles J. Bishop stole a Cessna 172, N2371N, and intentionally crashed it into the side of the Bank of America Tower in downtown Tampa, Florida, killing only himself and otherwise causing very little damage.
 * On April 6, 2009, a Cessna 172N, C-GFJH, belonging to Confederation College in Thunder Bay, Ontario, Canada, was stolen by a student who flew it into United States airspace over Lake Superior. The 172 was intercepted and followed by NORAD F-16s, finally landing on Highway 60 in Ellsinore, Missouri, after a seven-hour flight. The student pilot, a Canadian citizen born in Turkey, Adam Dylan Leon, formerly known as Yavuz Berke, suffered from depression and was attempting to commit suicide by being shot down, but was instead arrested shortly after landing. On November 3, 2009, he was sentenced to two years in a US federal prison after pleading guilty to all three charges against him: interstate transportation of a stolen aircraft, importation of a stolen aircraft, and illegal entry into the US. College procedures at the time allowed easy access to aircraft and keys were routinely left in them.
 * On November 11, 2021, Glen de Vries, co-founder of Medidata Solutions and Blue Origin space tourist, died in the crash of a 172 near Hampton Township, New Jersey.
 * On March 5, 2024, a 172M of 99 Flying School, 5Y-NNJ, crashed after colliding with Safarilink Aviation Flight 053, a de Havilland Canada Dash 8, near Wilson Airport over Nairobi National Park, killing the instructor and student pilot aboard the 172. The Safarilink flight landed safely with no injuries to the 44 people on board.

title: Cessna 172