Making changes to flights is so common that airlines actually overbook flights where possible, based on the assumption that a certain percentage of booked passengers will not actually make a particular flight. If more passengers show up than the plane can accommodate, the airline asks for volunteers to accept a voucher for a later flight. American Airlines issues approximately 250 such vouchers a day, as of February 2011. The airlines provides a number of options for re-booking your itinerary. The amount of time remaining until the flight takes off affects your available choices.

Flights Leaving Today

Call American Airlines at 800-433-730 to change your reservation with a representative over the phone. A change fee applies. Your new flight's scheduled departure must be within one to 12 hours of the time you call.

Use a self-service kiosk to change your flight if you are already at the airport. Swipe a credit card or personal identification, such as your passport, to activate the kiosk and locate your reservation. Follow the on-screen instructions to change to a different flight if one is available. A change fee applies, which you can pay via credit card directly at the kiosk. Print a new boarding pass from the machine.

Speak with any American Airlines representative at an airport counter if you are already at the airport. She can give you a list of options for flights to your destination leaving within the next 12 hours. A change fee applies, which you can pay directly to the representative. Ask for a new boarding pass if she does not offer you one.

Flights Leaving Anytime

Click on the "My Reservations" tab on the American Airlines homepage.

Login using your AA.com account credentials or locate the flight you wish to change by its record locator code. The record locator is six characters long and should appear on your itinerary confirmation paperwork.

Check the box to the left of the reservation you want to change. Click the "Change Flights" button. If this button is missing or greyed out, your flight is not eligible for online changes; you must contact the American Airlines reservations desk by phone.

Search for your new flight when prompted. Select your replacement flight and click "Continue." Confirm changes, and submit payment for any applicable change fees and/or difference in fares. Print your new boarding pass if your flight departs in the next 24 hours.

Tip

You may be exempt from paying a change fee if you booked an unrestricted, business or first class fare; if you are active military; or if you belong to certain levels of the American Airlines or a partner airline's frequent flier program.