Reader Mail: Explain How Airlines Come Up With Flight Numbers

Just before my Hurricane and Nor’easter induced break from Flying With Fish I received an email from Tim Wesolek asking, “can you [please] explain how airlines come up with flight numbers?”


Well Tim, there is no straightforward answer, but I will do my best.


For starters, some airlines have historical flight numbers, such as American Airlines’ Flight 1, operating daily between New York’s JFK International Airport and Los Angeles International Airport, or British Airways’ Flight 1, which previously was reserved for daily Concorde service between London’s Heathrow and New York’s JFK, and is now in service with British Airways’ all premium cabin service from London City Airport to New York’s JFK


Southwest Airlines is known to have some fun with its flight numbers.  Flight 1492 operates legs through Columbus, Ohio in honour of Christopher Columbus … and of course Flight 711 flies between San Antonio and the City of Lost Wages, Las Vegas. I don’t believe Southwest Airlines allows passengers to shoot craps on the flight, but I have a hunch that someone at Southwest from San Antonio likes shooting craps in Vegas.


Once you get past the specialty flight numbers, airlines create their own flight numbers, which tend to follow a logical system.  Flight numbering for airlines need to factor in not only the number assigned to the flight itself, but code-share flight numbers for flight operated by other carriers, as well as flights operating to-and-from origin and destination airports at the same time to eliminate confusion for controllers in The Tower.


Typically an airline uses flight numbers in blocks, for example 001 through 1999 are for mainline aircraft flights, 3000-3500 are for one regional carrier, 3600-3800 are for another regional carrier, 4000-4100 are for code share flights with one specific partner and 4300-4500 are for another code-share partner.


While some airlines will use the same flight number for flights in both directions of a route, such as Delta Air Lines’ Flight 5821, operated by Compass Airlines, flying both the north and south flights between Minneapolis, Minnesota and Kansas City, Missouri, most airlines use odd and even numbers to designate east-west and north-south flights. With many airlines, the ‘turn around flight’ is one digit off from the originating flight for flights flying between two of the same origins and destinations.


American Airlines, for example, uses odd numbers for North to South flights, and even numbers for South to North flights. American Airlines 2330 flies from Dallas to Chicago and turns around as 2331 flying from Chicago to Dallas.  Alaska Airlines flying west from Seattle to Hawaii with odd numbers, such as Flight 859 flying Seattle to Honolulu and even numbers on return flights, such as Flight 858 serving the Honolulu to Seattle route.


Are there exceptions to all the rules?  Absolutely. Are flights numbers regulated? Loosely by the International Air Transport Association (IATA), but ultimately this is how airline flights get their flight numbers. Through a complex system of making all the moving pieces in a jig-saw puzzle work, ensuring that when you board your flight it is clear what flight your flight number is to not only you, the passenger, but to The Tower, the baggage handlers dealing with mainline, code-share and regional airlines and to the schedulers and dispatchers that make all the moving pieces fit together.


Hope this explains it for you Tim.


Happy Flying!




  1. UA500 used to go to Indianapolis (from Chicago), but sadly no longer seems to. i suspect the merger was responsible for that, but haven’t flown it since 2008 so am not sure.

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