There's at least one ATL
flight that retains the same number:
In some respects, it does make sense, and is not much different than a flight number for an international flight being used on a domestic tag-on leg. I know that it used to be easy to decipher flight numbers, as airlines would assign certain flight numbers to their various regional carriers, but with airlines like Delta having so many different Delta Connection carriers than they had previously, those have been changed even further. I remember when EV
's flight numbers were all 4XXX, OH
exclusively used 5XXX, and I can't recall, but didn't OO
exclusively use 6XXX? This was well over a decade ago. I know that these days, flight numbers that were previously associated with one DL
Connection carrier are now among the range assigned to another DL
As previously noted, codesharing has contributed to this as well. Initially as part of an airline operating as a regional feeder for an airline and later as codeshare deals and eventually alliances took hold.