Originally Posted by
jragosta
I may be mistaken, but I don't think you can change an award ticket after you begin travel that day.
You can. If your award inventory is available on a flight (T for coach, U for biz, Z for first) then you can switch to that flight.
Finding a gate agent willing to process it for you is a different story altogether. Admirals Club and/or AA reservations are the go-to people for this request.