JetBlue started at a much more opportunistic time. VA is bleeding money. They're not successful in the money making sense. Spirit started in 1980, which also was a completely different era. How about Skybus, Champion, ATA, USA3000, Pace Airlines, Independence Air & soon to be Direct Air? All gone. Those are just a few examples. There are many more.

BTW, did you see all the failed airlines mentioned in the article Golden Bear posted? Many of those occured when gas was CHEAP.