To take part in the Delta SkyMiles rewards program, enroll for free by creating a SkyMiles account at Delta.com or at the airport. Once enrolled, travelers earn miles by booking flights, making purchases at over 100 retailers, booking accommodations through partner organizations, and completing other tasks.
Delta SkyMiles are redeemable for a wide range of rewards, including free flights, charity donations, and VIP sports and luxury experiences. To increase their account balances, customers can also transfer points from other programs, such as credit card rewards and hotel points, into Delta SkyMiles.
As of May 2015, miles earned through the SkyMiles program do not expire.