Go to your Jetblue interview and go with an open mind.
I agree AirTran is a great place, especially for someone wanting to live in the South. However, classes do get cancelled, and things change. You DO NOT have an ID yet.
You might just like JB. When I interviewed back in 01, several other companies were still hiring. Al Spain said he knew this was "a two way interview". JB wanted the right kind of folks, but that also meant they wanted folks to understand what the company was about. He told several anecdotal stories, including one about a guy who passed on an AA class to join the JB team after bringing his wife BACK to NY just to see the JetBlue staff at Kew Gardens.
I think you'll stick with AT, but you won't know if you don't go. Also...if you class gets rolexed until Jul, then Sep, then Dec...well...you will HATE yourself for not at least giving JB a closer look.
And...most important...if you get 2 offers you can live in the special "looking over your shoulder purgatory" that a bunch of folks are lucky enough (or unlucky enough) to experience.
Good luck in any case and thanks for your 20+ of service to this great county.