If you've made the reservation for the American Airlines flight 7 days prior to departure then there's usually no cancellation fee as long as cancel the flight 24 hours in advance before the flight is scheduled to take off.
If you didn't reserve the flight 7 days beforehand or cancel the flight later than the 24 hours then there's a cancellation fee of $110.00 for award flights, $200.00 for domestic flights and $400.00 cancellation fee for an international flight with American Airlines.