I agree with the post that says "Dont fix something that is not broken"..
Southwest has been flying the 737 its entire history and they have 30 years plus of profits to prove it.. Its a winner.. Dont stray or you will find yourselves in a big huge mess.
KISS - Keep It Simple Stupid..
Airbus.. The A320 family is pretty easy to work on.. But its expensive to purchase parts for and the wait can be painfully long. Each aircraft has its pros and cons. JetBlue seems to be doing quite nicely with the A320 and Southwest with the 737 Classic and the NG.
Personally US Airways made a huge mistake going the route of Airbus.. Not that its a bad plane but like anything at US Airways we did it 1/2 ass. We already had the 737-300/400 so why not go the route of the NG. Materials, procedures, Training, ground support, Tooling all would be similar or the same. One Pilot Group today would be flying all of the aircraft instead of the split groups we have.
Sure the A320 family is great if your entire fleet is Airbus.. But thats not the case at US Airways.. It would have been much better buying the NG and the 767-300/400 than to have purchases the Airbus A320 family and the A330..
Southwest, stick with your 737's.. Its a sure thing.