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Free Spirit, the frequent flyer program of Spirit Airlines, allows to earn miles every time you fly. You can earn Spirit miles using Spirit Airlines Mastercard which comes with a 15,000-mile sign-up bonus and gives 2 miles per dollar spent on every purchase. Spirit World Mastercard cardholders earn 100% of the miles flown when using the card to purchase flights.

Another way to earn more Spirit miles is to participate in partner programs. For example, you can earn additional FREE SPIRIT miles with car rentals as Hertz, Avis, with hotel chains like Choice Hotels and with other partners.

You can buy Free Spirit Miles for your award booking starting from $25 for 1,000 miles if you are short of miles. It is important to mention that this program is very restrictive as your miles expire after only three months of inactivity even if you are a cardholder.

While you might expect a co-branded Spirit credit card to be the best way to earn Free Spirit rewards, you would be mistaken. Travel rewards cards that allow you to redeem points toward any travel purchases, not just those made with one airline, and have generous rewards, seem to offer more. For instance, the Discover it® Miles card offers unlimited 1.5x miles on all purchases. All the miles you’ve earned at the end of your first year will be matched (providing you are a new card member). For example, if you earn 35,000 Miles, you get 70,000 Miles.

You can redeem Discover miles for any travel expenses, including airline tickets, hotels, cruises, rental cars and more. This card comes with no annual fee and no foreign transaction fee. Rewards have no expiration date.

As you can see, applying for an airline co-branded card is not always a good idea. Choose card with great rewards, first-year miles match and flexible redemption options, like the Discover it® Miles, to earn enough miles for your next travel.