Allegiant Air makes it a snap to rack up miles through its Allways Rewards program. Flying with the airline, car rentals and hotels are a few great ways you can earn airline miles, in addition to buying flights. When booking your airline tickets with Expedia, locate your loyalty program in the dropdown menu. You can then key in your membership number to work out if your booking is eligible. Save your dough, score miles and tick off more destinations with Expedia!