# Is there a mathematical formula for flight numbers? **URL:** \ **Category:** Factual Questions\ **Created:** [June 19, 2014, 5:57pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155 "2014-06-19T17:57:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [June 19, 2014, 5:57pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/1 "2014-06-19T17:57:41Z")
This is a hypothetical. I do not necessarily need a quick answer. If I am traveling somewhere and forget my flight number, would it be possible to pull out a calculator and figure it out? ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [June 19, 2014, 5:59pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/2 "2014-06-19T17:59:51Z")
I doubt it. But a smart phone would be able to look it up by route and approximate departure time. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [June 19, 2014, 6:01pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/3 "2014-06-19T18:01:51Z")
No, how would that even work? Flight numbers are **nominal numbers**. You can’t do math on them. They are simply assigned by the airlines any way they see fit. Could you figure out someone’s license plate number with a calculator? Same thing. “Nominal numbers (sometimes called categorical numbers) are numerals used for identification only. The numerical value is irrelevant, and they do not indicate quantity, rank, or any other measurement.” [https://www.google.com/search?q=what+are+nominal+numbers&oq=what+are+nominal+numbers&aqs=chrome..69i57.4064j0j1&sourceid=chrome&es\_sm=93&ie=UTF-8](https://www.google.com/search?q=what+are+nominal+numbers&oq=what+are+nominal+numbers&aqs=chrome..69i57.4064j0j1&sourceid=chrome&es_sm=93&ie=UTF-8) ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [June 19, 2014, 6:55pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/4 "2014-06-19T18:55:09Z")
There’s no formula, but there are a few rules, which are never 100% adhered to. Most airlines assign odd numbers for one direction (north, east) and even numbers for the other (south, west.) “Flagship” routes, e.g. New York to London, will tend to have single or double-digit numbers, with neighboring even/odd pairs for the round trip. Four digit numbers are usually codeshares or regional carrier flights. Numbers in the 9xxx range are often used for irregular operations, such as equipment moves after a weather event. ---
**Author:** ![ElvisL1ves](https://avatars.discourse-cdn.com/v4/letter/e/5daacb/32.png) [@ElvisL1ves](https://boards.straightdope.com/u/ElvisL1ves)\ **Post date:** [June 19, 2014, 7:10pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/5 "2014-06-19T19:10:07Z")
And airlines normally retire the number of a flight that crashes. ---
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [June 19, 2014, 7:23pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/6 "2014-06-19T19:23:49Z")
I think the idea behind the OP is that a flight number could be calculated based on some sort of formula that you could take and plug in the origin and destination (e.g. by latitude and longitude, some cipher conversion from the airport abbreviation (e.g. IAD), etc.), the time of day of the flight, the day of the week or the day of the month that the flight leaves, and/or some numeric id associated with the airline. E.g. convert origin and destination airport codes to numbers based on A=1, B=2, etc., add them together, then multiply by the time of departure in UTC, then divide by the day of the week (Sunday = 1, Monday = 2, etc.), then subtract the airline’s corporate registration number at its applicable corporate location of incorporation. I think the answer to the question is no, they don’t do that, at least on any systemic basis. ---
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [June 19, 2014, 9:22pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/7 "2014-06-19T21:22:13Z")
How _are_ flight numbers assigned then? I always thought they were fairly permanent. This particular plane is always Flight XXX, unless it’s operating under another airline, in which case it will have a different number for that airline. But when it goes back to the first airline, it’s XXX again. But that’s little more than speculation on my part. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [June 19, 2014, 9:26pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/8 "2014-06-19T21:26:52Z")
It has nothing to do with the particular plane. (Each airplane does have a unique tail number, but that’s unrelated to the flight number.) Different equipment, even completely different types of airplanes, may be used for flights of the same number on different days. ETA: One universal rule is that the same flight number is never used twice in the same day. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 19, 2014, 9:35pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/9 "2014-06-19T21:35:12Z")
> [@](#): > > ETA: One universal rule is that the same flight number is never used twice in the same day. Yes and no… I’ve been on flights that were “To city Y via city X”, or “to X with continuing service to Y”, where the passengers going all the way to Y had to change planes in X. So there was one airplane going from W to X, and then another airplane going from X to Y, but both had the same flight number. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [June 19, 2014, 10:05pm UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/10 "2014-06-19T22:05:34Z")
> [@Chronos](#): > > Yes and no… I’ve been on flights that were “To city Y via city X”, or “to X with continuing service to Y”, where the passengers going all the way to Y had to change planes in X. So there was one airplane going from W to X, and then another airplane going from X to Y, but both had the same flight number. And that’s a single flight. For a large definition of “flight.” ---
**Author:** ![Tim\_R.Mortiss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim_r.mortiss/32/142_2.png) [@Tim\_R.Mortiss](https://boards.straightdope.com/u/Tim_R.Mortiss)\ **Post date:** [June 20, 2014, 12:16am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/11 "2014-06-20T00:16:05Z")
Sometimes they are assigned whimsically. I remember walking around at O’Hare one day and seeing Flight #711 to Las Vegas, and further down the terminal, Flight #1492 to Columbus. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [June 20, 2014, 12:35am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/12 "2014-06-20T00:35:21Z")
> [@Shagnasty](#): > > No, how would that even work? Flight numbers are **nominal numbers**. You can’t do math on them. They are simply assigned by the airlines any way they see fit. Could you figure out someone’s license plate number with a calculator? Same thing. > > “Nominal numbers (sometimes called categorical numbers) are numerals used for identification only. The numerical value is irrelevant, and they do not indicate quantity, rank, or any other measurement.” > > [what are nominal numbers - Google Search](https://www.google.com/search?q=what+are+nominal+numbers&oq=what+are+nominal+numbers&aqs=chrome..69i57.4064j0j1&sourceid=chrome&es_sm=93&ie=UTF-8) This is not quite true if you include license plates as nominal numbers. In CT for example, we recently completed going through the sequence ### LLL. These were released approximately in order alphabetically through the letter sequences and within that in numerical order for the three digits. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [June 20, 2014, 1:03am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/13 "2014-06-20T01:03:57Z")
> [@OldGuy](#): > > This is not quite true if you include license plates as nominal numbers. In CT for example, we recently completed going through the sequence ### LLL. These were released approximately in order alphabetically through the letter sequences and within that in numerical order for the three digits. Can you calculate it though given other information or do you have to have a lookup table to match it with a vehicle or person? I am sure it is the latter. Almost all businesses and government entities have rough strategies for everything from barcodes to Social Security numbers. They tend to use certain ranges for certain things and sometimes the have extra information for a series of digits but that doesn’t mean that they aren’t nominal numbers. You can’t do math with them them and they could have used a series of letters for them just as well. There is no way to determine what an individual code or license plate is without using a lookup table rather than equation. Can you do a math equation to determine a particular CT license plate without using any other arbitrary nominal numbers that have to be looked up themselves? ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 20, 2014, 1:06am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/14 "2014-06-20T01:06:41Z")
> [@OldGuy](#): > > This is not quite true if you include license plates as nominal numbers. In CT for example, we recently completed going through the sequence ### LLL. These were released approximately in order alphabetically through the letter sequences and within that in numerical order for the three digits. But that sounds like it’s sequential, not something that could be figured out through a formula. Contrast that with Illinois’s drivers license numbers, which can be figured out if you know somebody’s first name, middle initial, last name, date of birth, and gender. Those are formulaically generated. (Though you do need a table for first names to get the right values.) ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [June 20, 2014, 1:18am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/15 "2014-06-20T01:18:21Z")
> [@pulykamell](#): > > But that sounds like it’s sequential, not something that could be figured out through a formula. Contrast that with Illinois’s drivers license numbers, which can be figured out if you know somebody’s first name, middle initial, last name, date of birth, and gender. Those are formulaically generated. (Though you do need a table for first names to get the right values.) Even that wouldn’t be 100%. In numbering schemes like that, you have to allow for exceptions for duplicates. It wouldn’t happen often but same-sex twins could cause an issue (I am not sure if it tries to do some weird strategy for twins with a first name for twins starting with the same letter to differentiate them but you have to account for such things). Even random strangers could trigger a duplicate as a fluke and that isn’t allowed for license plates. That kills the whole math idea for any software package and forces you to use a lookup table rather than a simple equation. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 20, 2014, 1:27am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/16 "2014-06-20T01:27:40Z")
> [@Shagnasty](#): > > Even that wouldn’t be 100%. In numbering schemes like that, you have to allow for exceptions for duplicates. There are duplicates in the IL drivers license numbering system, for that exact reason. [Read here](http://www.highprogrammer.com/alan/numbers/dl_us_shared.html). > [@](#): > > Illinois may have overflow digits, but if they do the information is not on your driver’s license. This means that if Joshua William Smith is wanted by police and his driver’s license number is flagged as such, Jack Wayne Snoddy may be briefly detained while the police check their records to sort out the shared number. I have been told that Illinois state databases actually include a two or three digit number to distinguish between different people with the same license. One correspondent told me that their friend was pulled over for a minor traffic violation and was arrested as someone else. He sat in the police car for a while while they sorted it out. He and the other person had the exact same number; the other guy was a wanted man, but my correspondent’s friend did not. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [June 20, 2014, 1:33am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/17 "2014-06-20T01:33:39Z")
Interesting, that is a weird system. You can calculate your driver’s license number but it may or may not be the whole one. Only the police know that. It is still a nominal number however even if it is straightforward and hidden to most people. The police can see the full number but the average person doesn’t know if they have an evil twin out there somewhere. Only the database lookup table can tell them apart. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [June 20, 2014, 1:37am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/18 "2014-06-20T01:37:44Z")
> [@Shagnasty](#): > > Interesting, that is a weird system. You can calculate your driver’s license number but it may or may not be the whole one. Yep, it is odd. It’s not certain there is an overflow system in Illinois. That’s just a guess on the website’s part, and I’ve heard that there isn’t–they just go an extra step and check the name and address along with the drivers license number. I wouldn’t know for sure. But given any name and date of birth, you can calculate your Illinois drivers license ID. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [June 20, 2014, 2:39am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/19 "2014-06-20T02:39:00Z")
When I encrypt my name and birthday using a certain popular encryption algorithm, I get my ZIP code. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [June 20, 2014, 2:46am UTC](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155/20 "2014-06-20T02:46:57Z")
> [@Shagnasty](#): > > Can you calculate it though given other information or do you have to have a lookup table to match it with a vehicle or person? > [@Shagnasty](#): > > “Nominal numbers (sometimes called categorical numbers) are numerals used for identification only. The numerical value is irrelevant, and they do not indicate quantity, rank, or any other measurement.” No you can’t calculate a CT license plate number, but I was replying to the statement that “they do not indicate … any other measurement.” They do. They indicate the order in which they were issued and hence their approximate age. I still have a ### DLN plate which was issued around 1985 and transferred with two trade-ins. The fact that I see almost no other plates anywhere near that old tells me most people apparently don’t trade in one car at a dealer for another but buy a car then sell their old one elsewhere. [Next page](https://boards.straightdope.com/t/is-there-a-mathematical-formula-for-flight-numbers/691155.md?page=2)