I don't think that the aviation industry can handle anymore of the nonsense the TSA
and "Homeland Security" are shoving down their throats.
Its pretty obvious that the "classic" business model, if you will, of the mainstream airlines is now obsolete. The low-fares found a new way to fly and make money at it. This is an international trend, not only affecting US carriers. In Brazil, Gol (our low-fare) is really bothering the main carriers (Varig and TAM) who say they'll merge, but at the same time do everything possible to delay this merge.
The costs are just too great. The airlines need efficient business plans and the old airlines never really adapted to the new times, hence the difficulties of United, American, Continental, US Airways, Varig, TAM, Alitalia, Air France, TAP Air Portugal, etc.