If you've already paid up your fare for the flight and need to change the flight on American Airlines for a regular flight then the cost to change the flight will be $200.00
If the flight on American Airlines is for international then it will cost you $750.00 to change the flight.
Same day flight changes for economy flights are between $75.00 to $150.00 and if you're a first class passenger or business flight then the cost to change the flight is free.