Originally Posted by
gooselee
There is an actual breakdown out there somewhere, but generally yes, there is a taxonomy.
IIRC the 5000s are all DL connection flights. 9000s are charters. Some other 4-digit range is reserved for code shares (DL marketed but operated by a partner).
In general the most "important" intl flights get lower flight numbers. I think all two-digit and many three-digit numbers are intl?
9000s can also be non-revenue ferrying flights.
From what I've seen:
GoJet: 6000s,
Endeavor: 3000s
Shuttle America: upper 2000s to lower 3000s.
Compass: 5000s
SkyWest: 4000s, 7000s
Mainline: 0001-2999
Not going to try with all the various codeshares haha. My KLM flights have generally been in the 9000s though.