I think all eyes are on Mesa and Frontier.
Mesa has been losing money badly. They just lost a 36 airplane contract with Delta. Mesa's performance for United Express has been abysmal. United has been picking up Mesa's slack with TSA and XJT. US Air has made it known that they do not forsee Mesa as a codeshare in the future. Pilots are leaving in mass quantities (what, 700-1000 pilots left last year, many of them making lateral moves). They lost an $80 million dollar lawsuit to Hawaiian. I believe Aloha's creditors can still sue Mesa. Pilots contract is up for negotiations, and they will not settle for an industry worst contract again! Their stock just got delisted from the S&P 500 (I think they are at about $1/share). Mesa will fail soon, and this will be good for the airline industry as a whole.
Frontier is a one hub airline. Almost every single one of their flights either departs from or arrives in DEN. United Airlines (the world's second largest airline) has their second largest hub in DEN, so Frontier is not even the largest airline at their major airport. Second, the entrance of Southwest into the DEN market has put tons of pressure on Frontier. They have sold several of their A319's (maybe some were A318's...). Lynx, their start up regional airline, has cost a lot in start up costs.
Both airlines have a decent amount of cash on hand, but this is the airline industry.
I am curious to see the first quarter earnings for all airlines. This will be a good glimpse into the future, since the price of oil will not be coming down.