A frequent-flyer program is offered by an airline to reward its customers for loyalty. People who are part of the program usually earn miles (frequent-flyer points). These miles can be redeemed (exchanged) for free flights or other products and services. Many airline alliances allow customers to earn and redeem miles with a number of airlines. This may also work with a codeshare agreement. The first airline to launch a frequent-flyer program was American Airlines.