Sir Richard Branson's Virgin Group is to receive a major windfall by selling down part of its stake in Virgin Atlantic in a major joint venture deal set to include Air France-KLM and existing investor Delta Air Lines.

Air France-KLM is to buy a 31pc stake in Virgin Atlantic for £220m.

Virgin will hold on to a 20pc stake in the trans-Atlantic airline, and hold onto the chairmanship, as a result of the deal which will see a closer union between the four airlines.

Delta, which bought a 49pc stake in Virgin Atlantic from Singapore Airlines in 2013, will at the same time buy a 10pc stake in Air-France KLM for €375m, gaining a seat on the board of its European counterpart.