dbaker,

About two years ago I checked in for my AA flight 74 minutes prior to departure... it was an international flight and the policy was to close the flight 60 minutes in advance. It was oversold, and when I reached the gate I was denied boarding (no compensation) because I checked in "too late." They were unable to rebook me on another flight that day, so my ticket became worthless. I unsuccessfuly argued the charges and had to take AA to small claims court, where they presented "evidence" that I checked in too late. Problem? I had a TIME STAMPED boarding card... keep in mind that AA was willing to go to small claims court over a $400 ticket.

The airlines (maybe not UA ) take their money very seriously.