FREE SPIRIT members earn miles on flights and on partner purchases through Choice Hotels, several car rental companies and dining partners. Round-trip award tickets start at 5,000 miles with extra savings during off peak periods.
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Points never expire with Southwest Airlines Rapid Rewards so long as there's a flight or partner earning activity every 24 months. Southwest offers some 3,900 flights daily, and with no blackout dates and unlimited reward seats, redeeming points is easy. Rapid Rewards members can also earn points on car rentals with Alamo.
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While Flying Blue is the loyalty program for two European airlines, it does offer appealing benefits for American flyers as well, including the ability to earn and redeem miles through SkyTeam airlines and a wide variety of hotel and retail partners. Flying Blue points can also be transferred to and from Chase Ultimate Rewards, Citi ThankYou Rewards, Hilton HHonors and American Express Membership Rewards.
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Aeroplan miles can be earned by flying to some 1,200 destinations worldwide through Air Canada and Star Alliance partners, as well as by shopping with partners online. Altitude, Air Canada's tiered frequent flyer program, offers passengers a chance to earn Qualifying Miles to go toward flights, upgrades or Aeroplan rewards.
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SkyMiles members earn miles with flights on Delta and several partner airlines, as well as through Delta Vacations getaways or through myriad hotel, car rental, restaurant and retail partners. Miles never expire and can be used to book travel on Delta or partner airlines, purchase cabin upgrades or shop on the SkyMiles Marketplace.
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AAdvantage miles can be earned and redeemed on both American Airlines and oneworld partner airlines. Miles can be redeemed toward flights, hotels, upgrades and retail products, and they can be earned through more than 1,000 partner companies. 
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Fliers from across the West Coast and major transportation centers throughout the United States can benefit from Alaska Airlines' Mileage Plan. Passengers earn miles on every flight, as well as on eligible flights with 15 partner airlines and by booking stays with 11 different hotel partners. Points can be used for booking free flights or cabin upgrades.
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United's MileagePlus program is excellent for domestic and international travelers, who can earn and use points with United and more than 30 partner airlines to access over 1,000 destinations around the globe. Besides booking travel, rewards points can go toward hotels, car rentals, cruises, shopping or dining.
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TrueBlue, JetBlue's loyalty program, offers flexible points redemption with no blackout dates or seat restrictions. Passengers earn points on JetBlue flights (bonus points for flights booked through the JetBlue website), as well as flights with six partner airlines, and points never expire. Family Pooling gives families a single shared account to accrue points faster.
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HawaiianMiles members enjoy reduced baggage fees when traveling between islands and can earn miles on flights, hotels and shopping with partner vendors. Miles can be redeemed for flights on Hawaiian Airlines or its partners (including Virgin America and JetBlue), as well as on hotel stays and car rentals.
Photo courtesy of Hawaiian Airlines