http://www.usatoday.com/travel/colum...d-flight_N.htm
"American does have a flat-tire rule for customers who call the airline to advise that they won't make their flights, according to representative Tim Smith. This call must come in no more than two hours after the flight's scheduled departure. But that doesn't guarantee them a spot on the next flight out: Passengers travel on a standby basis only."
USA Today: Source