+1 on this post. I moved around and flew for several airlines. At the time, they all seemed like big moves. In retrospect, a few years here or there isn't all that significant in the long run. So if you can go to somewhere that boosts your resume, it's worth it, providing it's also somewhere you would rather spend a career at should plan A not work. The JetBlue example was used. Keep in mind that SWA was a second tier job at one time and now they are a first tier career choice. I could see JetBlue doing the same thing (providing they vote in a union!

)
The only thing you can be sure of is every airline will change dramatically over a 25 year time, so it's all crap shoot.