STOCKHOLM—Scandinavian airline SAS says it plans to order 12 new planes from Airbus in a deal valued at $3.3 billion at list prices.

SAS said Tuesday it has signed a memorandum of understanding—short of a firm order—for eight A350 and four A330 planes as part of a renewal of its long-haul fleet.

The deal also includes upgrades of seven older jets and an option to purchase another six A350 aircraft.

SAS said the A330s will be delivered in 2015 and the A350s in 2018.