Originally Posted by
JnsV
I was only able to find out the record locator with AA flight numbers by logging into my AAdvantage account, going to My Reservations/Flight Check-In and finding my reservation by supplying my name, date and the AA code for one of the AA operated (but partner coded) flights in the reservation, but NOT the booking reference.
Bingo. Since the flight is AA-operated, AA does have access to change seat assignments. The way I got it done in the past was for an agent to look it up by flight number, date, and last name. If it works self-service too, even better.