Originally Posted by
trooper
What he said...
..Airlines do a lot of this... best example I've seen was a flight I took from DEN-CEZ... as far as I am aware it operated as
ZK XXX,
UA XXXX and
F9 XXXX..
Three different flight numbers... and only 19 seats!

You may want to check out some of BD's flights for example. 10+ codeshares are not uncommon.