Originally Posted by ijgordon

Well, beginning 100 hours before departure, EXPs may begin to get upgraded, thus freeing up additional seats in the back. These are sometimes desireable exit row seats, which you can only grab if you are elite yourself, but they may be general seats that you can get as well. Just keep checking your reservation on AA.com.
If the flight ends up oversold, and you don't have a seat assignment, you'll be at the top of the list to be bumped. Some people go out of their way to make that happen...