Thanks for the replies everyone..it really was an honest mistake. I even had it in my mind the morning before the interview, and thought about it as soon as I was filling out some paperwork post-interview.

I know you guys, and the HR dept will think it's BS that I claimed to forget, but from what you said, Rick, it sounds like I should call and be honest before getting into class and having the chance of being fired.

I did not claim to have a degree of any kind on my resume..and on airline apps, I said I was in college for 1.5 years (which is true) and I checked that I did not graduate. I guess my next question is if my transcripts/grades are soemthing that is given out to these background checkers. Or if they see dropping out of college as something to rescind the offer.