candidate: Flight 77 , flying at 530 mph ( 853 km / h , 237 m / s , or 460 knots ) over the Navy Annex Building adjacent to Arlington National Cemetery , crashed into the western side of the Pentagon in Arlington County , Virginia , just south of Washington , D.C. , at 09:37:46 , killing all 64 people on board ; 53 passengers , five hijackers , and six crew .