Frequent-flyer programs are rewards programs set up by airlines. They give you special benefits after you fly on their airline a certain number of times. When you join a frequent-flyer program, the airline will give you a unique membership number. Every time you fly with that airline they will keep track of how many times you've flown with them. After you've reached a certain number of flights, the airline will give you a reward, like free flights, discounts, or special privileges.