Delta says it will form a joint venture with Virgin Atlantic, where the two airlines would share money from the flights operated under the partnership.
Sir Richard Branson will still own more than half of Virgin Atlantic, which will continue to fly as a separate airline under its own name.
Landing rights at London's Heathrow Airport are limited. So buying part of Virgin Atlantic will help Delta get a bigger piece of the travel market there.
The joint venture needs approval from U.S. and European regulators. Delta is aiming to have the joint operation running by the end of 2013.