I guess I don't get your point. If there was 10 minutes warning that a "hostile" 747 was heading to New York, I doubt if it would be intercepted before it arrived in Manhattan. Unless they happened to be on patrol, it takes longer than 10 minutes to scramble and have them in the air. Now, assume I am wrong, and they met the 747 while it was still over New Jersey, with about 300 innocents on board. If they shoot the aircraft the 300 will die, plus a large number on the ground. (As I said, a mass the size of a 747 does not just turn into a cloud of harmless dust). Or are you assuming that they would do an inflight "Pitt Manuver" on the plane and gently guide it to the ground?