Lets be honest, products and individual customer experiences vary with the direction of the wind, the customer service agent you deal with and the crew in the aircraft. These are facts.
Delta: in BK, a take over target.
United: still in BK after how many years, I forgot?
Northwest: in BK
America West: once in BK
US Airways: once in BK bought by America West, combined operation solvent making money
Continental: in BK many years ago, in pretty fair shape now, considered a survivor. Making money.
AA: Never in BK, has survived post 9/11 in good shape and has not walked away from any employee benefits, including pensions, which have all but been removed from every other airline. Making money.
Southwest: Making money only because of it's fuel hedges. If they paid what AA and NWA pays for gas they would be losing money hand over fist. What does that say about their current operations? Does that make them a better airline operation or just better investors.
JetBlue: Things are not going well. In the last couple quarters every airline has done better. The ones losing money lost less and many are in the black. Some how, JetBlue is doing worse. Quarterly loses, stock down, reduced growth, rejecting Airbus orders for smaller jets. Let's see, new airplanes that are extra fuel efficient and under warranty, employees still at the 1-4 year step on the pay scale ( lower labor costs over legacy carrier) very favorable press and seemingly very good customer satisfaction. How is it that Continental can pay it's people much better, fly older less efficient aircraft and provide expensive services on their international routes and still make money when JetBlue can not?
Bottom line, they are all safe and generally provide good service. Just shop and buy the lower fare. Keep in mind that saving just $10 can cost you a $100 in headaches if you do not do your homework.
