Fadec
I know many have some really serious obligations and moral issues of leaving one firm for another (not to mention burning bridges), but never forget this is a Senority based system. Those few week you delayed getting hired means someone else will get your captain bid, base opportunities, weekends off, or worse a furlough notice.
I always recommend take the job as soon as possible, that is if you really want it. So remember, your delay is some else's gain.