Originally Posted by
PBIGuy
Keep in mind that there aren't 9,999 AA flights, but with codesharing, several flights have multiple numbers in the system. Delta does the AAA-BBB-AAA same number system on many of their flights as well. US used to do this on some of their express flights - not sure why as I'm sure there were plenty of numbers to go around back then. But I do recall seeing that I was checked in as sequence 75 on a 50-seat flight once and that confused me (because the first 50 were on the inbound flight and I was on the outbound).
I remember reading that Air Traffic Control systems can't handle numbers above 9999.
I guess there must be an internal hard-coded limitation as well. Otherwise, the logical solution would be to use a fifth digit to designate codeshares. For example, flight 1XXXX could be the AA codeshare of BA XXXX, 2YYYY could be the AA codeshare of IB YYYY, etc. This would enable AA to use the full 9999 numbers, and it would make things much clearer for travelers on codeshares as well, because those who knew the system wouldn't have to keep track of 2 flight numbers.