Four huge airlines on three continents want to create a virtual super-airline. They plan to spend more than $1 billion to do it. In a series of transactions announced Thursday, Delta Air Lines (DAL) and Shanghai-based China Eastern (CEA)are each buying 10% of Air France/KLM (AFLYY)Group. And Air France/KLM will buy 31% of Richard Branson's Virgin Atlantic Airways. The roughly $1.2 billion worth of investments will deepen business ties between the carriers, giving them the ability to coordinate across the busy air corridor between Europe and the United States.