Southwest makes money because they have their fuel hedged better than anyone else, without the hedge they are losing money. And their hedge will be over soon, and they know it, which is why they just raised all their fares this week. Jet Blue ain't making money. Air Tran is much better run than Jet Blue.
Correction -- Southwest only raised the high maximum for last-minute purchases. That reportedly amounts to about 2% of their fares, as only a tiny minority of customers purchase their tickets last-minute ... I have flown Southwest for many years and have never bought one of those near-term fares, and probably never will.