The only thing I'll say is if you hadn't made up your mind, why did you apply to UPS? If you have been hired and say no, I don't think they'll ask again (from what I hear). So the fact that you applied to UPS, went through the process and was hired means to me that in the back of your mind you think you should go to UPS.
Why not JetBlue, SWA, etal.?