As others have said, dodge duck dip dive and dodge, at all costs. Right now you're nothing more than a "maybe." You need to get into a class and get a seniority number before you have any protection. That year (or however long your deployment will be) will have a downstream effect on the rest of your career. Call in all favors, donate a kidney or offspring, volunteer for an even worse deployment in two years. If your front office is cool explain the situation and see if they can help. Depending on what pool you're swimming in, you may loose your spot. If it does come to pass that you can't get out of it, then work with the hiring at whatever airline you're at and see what you can do to stay in the pool.