13. This airline operated the only daily nonstop 747 service between Washington Dulles and Chicago.
I'm guessing this is United.
Sorry, guess again...
My guess is that this was Northwest, a 747 routing New York JFK-Washington-Chicago-Tokyo. Not particularly competitive with Pan Am's pioneer nonstop (well, on a good day with a following wind, and if things still looked good when approaching Anchorage) flight from New York to Tokyo of those times, and I presume in the "old days" the fares were the same and interchangeable on all carriers.