Originally Posted by
GrayAnderson
I think you'd have more luck doing a "callsign split" for a large enough operation than adding numbers. It just slows down communication that much more to have the extra number (remember, standard format for reading numbers will be [for example] "Speedbird Two Four Three", not "Speedbird Two Forty-Three").
For ATC purposes you already have that to some degree. The regionals use the callsign of the operating carrier (For Delta Connection those are Endeavor, Brickyard and SkyWest).
How many flight numbers are wasted on codeshares?