Summary
- Flight numbers are close to running out, posing challenges for airlines.
- American Airlines recently extended their mainline flight numbers past 3000.
- Solutions, like abbreviations and introduction of alphabets, are being considered to address flight number limitations.
Numbers stretch up to infinity. But this is not the same for flight numbers. We have some unforgettable flight numbers, such as the MH370, associated with the extraordinary disappearance of a Malaysian Airlines flight, or the BA001, which British Airways used for its Concorde services. Some numbers, such as 13 or 666, are tacitly agreed to not be used for flights.
Flight numbers aren’t too long, either. It would be impossible to find someone who has seen a flight number that was more than four digits long. Even within the existing limitations of the maximum of four digits used for flights, some numbers (generally the ones above 9000) are reserved for ferry flights, while others are used for codeshare flights.

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With the operations of airlines getting bigger by the day, one has to wonder if carriers are ever going to run out of flight numbers. And if they do, what solutions exist?
Photo: Jonathan E. Hendry | Simple Flying
Airlines are actually close to running out of flight numbers
Close to half a decade ago, Indian aviation authorities were concerned that the growth of aviation in the nation and the resulting dearth of flight numbers was a serious issue to be looked at. Times of India has reported about the possibility of an impending safety issue due to the three-digit codes used in flights in India:
“The existing three-digit codes are increasingly leading to confusion and there has been a spate of safety scares when similar sounding flight numbers operate to or from the same airport around the same time — something that’s happening with increasing frequency due to the volume of traffic.”
Photo: Leonard Zhukovsky | Shutterstock
Flights in the US, however, use a maximum of four digits for their flights. American Airlines, the flag carrier of the USA, operates 6700 daily flights. Given that there are 9999 digits to choose from, one might feel that the problem isn’t too much to worry about. However, there was a report that said that an American Airlines’ recent meeting saw a discussion around the possibility of running out of flight numbers. A worker in the IT (of the airline) pondered whether resorting to a five-digit number was the way forward.
There have been extensions to the limitations on the flight numbers used
In 2019, The Points Guy reported that AA actually had a limitation of 2,949 flight numbers they could use for mainline flights:
“At American, flights 1 to 2949 are all assigned to the mainline fleet while 2950 to 6099 are all reserved for swaths of regional partners such as Skywest or Envoy. Delta and United use a similar formula. This helps route planners and other staff quickly identify which carrier is operating a flight and often where it’s headed.”
Photo: Markus Mainka | Shutterstock
However, in April of this year, this changed as American Airlines extended the flight numbers they were using, with mainline flight numbers extending to 3,139. A few examples of this included:
- AA30006 was used on American’s flights operated from Raleigh–Durham International Airport (RDU) to Phoenix Sky Harbor International Airport (PHX) on their Boeing 737s.
- AA30009 was used on American’s flights operated from Eagle County Regional Airport (EGE) to Dallas-Fort Worth International Airport (DFW) on their Airbus A319s.
- AA3001 was used on American’s flights operated from Los Angeles International Airport to Louisville Muhammad Ali International Airport (SDG) on their Airbus A321s.
But extending numbers to flights isn’t as simple
One might wonder why the question of running out of flight numbers is such a big deal. After all, we could extend a three-digit flight number system to four, and the four-digit flight number to five, and so forth. However, the solution isn’t as simple as it seems. Viewfromthewing.com reported that the solution would require an update on the systems that airlines have been using for more than half a decade:
“The computer systems airlines use are built on top of systems that are built on top of systems that date back sixty years. So it’s hard to adjust for this. And, as with Y2k*, older systems economized on data size for storage and processing reasons.”
*The Y2K problem refers to the (potential) computer problems that were associated with calendar data after the year 2000 kicked in, as many programs represented four-digit years, such as 1900, with the final two digits: 00. This made it difficult for computer programs to distinguish the year 1900 from 2000.
Using abbreviations, and other solutions
The problem with running out of the four-digit limitation on flight numbers doesn’t quite exist (at least for now) except for American Airlines, Delta Air Lines, and United Airlines. Much like the phrase “year 2000” could be economically written as Y2K, United used the abbreviation system for the nomenclature of their elite status, reported viewfromthewing.com:
“ Abbreviations were used. For instance that’s how United Airlines elite status levels got their names, “1K” was used instead of 1000K or 100,000 mile status because they only had two digits to designate it. It was meant as an internal tag, not to be public with customers, but it eventually stuck.”

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Perhaps a solution like this could be on the cards. The other solution could be assigning the same flight number to more than one daily flight. But this could lead to problems, such as those seen in India a few years ago. After multiple flights were assigned the same numbers, the joint DG and head of Safety at DGCA had to flag the issue publicly:
“Even after detailed deliberations on call sign conflicts during last season, airline operators are filing new flights in the same route within a 15-minute gap, with similar call signs. They were advised to take cognizance of guidelines on the call sign conflict issue”
Photo: China Southern
As aviation becomes accessible to more people, resorting to increasing the three-digit flight numbers to four-digit ones, or four-digit flight numbers to five-digit ones might be the only reasonable solution. And so can the introduction of alphabets. But the aviation community is keeping an eye on when this technological change will come about.