LONDON CALLING: Delta Air Lines Inc. is said to be eying a stake in Virgin Atlantic in large part because of Virgin's status as the second-biggest airline at London's Heathrow airport.

NO FLY-BY-NIGHT: The New York-London market is one of the world's most important airline routes. Delta has a strong presence in New York but is weaker than its U.S. competitors on the London end.

BIRDS OF A FEATHER: American and British Airways cooperate on flights between New York and London. And United Airlines already has a relatively strong presence on that route.