Delta's new cabin design is set to debut on a Boeing 757 then an Airbus A350 (pictured).Courtesy of Delta Air LinesDelta Air Lines is set to update the cabins of its Boeing 757 and Airbus A350 jets.The 757s being updated are at least 20 years old as Delta waits on delayed new 737 jets.New cabins feature memory foam cushions in economy plus a refreshed business class.Delta Air Lines unveiled a new cabin design on Tuesday.It's set to debut on a Boeing 757, operating short-haul routes, later this fall.