CO allows free standby for later flight if you missed the booked one. (From Amex web site summary). AA should do that at least.


Effective January 1, 2003 (and not until that date), a new standby procedure for non-refundable fares will take effect. A $100 change fee will be instituted for any passenger that wants to standby for an earlier/later flight. Exception: Any passenger that presents themselves at a Continental Airport Ticket Office within two hours after his/her original departure time will be allowed to standby for the next available flight at no additional charge.