Originally Posted by Tropical

I disagree with what the others said. I don't think they're likely to work with you unless it's military, or some sort of family emergency.

You filled out your availability on the application. They questioned you about it again in your interview. The CJO letter clearly spells out its validity timelines.

You can't just change your mind because you got a better offer, and expect Delta Air Lines to wait around for you. The company needs people now, and if you can't uphold your end of the agreement, they will just move onto the next person. In fact, I think it kind of speaks volumes about your personal integrity and work traits to try and change the deal after the fact (unless it's a military commitment or emergency). Perhaps an error was made.