AWA and SWA made money in LAS at 7 and 8 cents/seat mile. US Airways at 14 cents/mile cannot. National did not make money with the 757s.
AWA did run 747s between LAS and JFK and PHX and JFK. We did not make money on those routes with the 747 because the costs were too high for the yield. And the jets were full for the most part. It is easier to fill 150 seats and get the price you need (yield) than trying to fill 400 seats at a whack.
See also Tower Air for failed 747 pax ops.
I wondered whose 767 that was in FLL. I thought it was Amerijet's.