Firefighters with Commander, Navy Region Japan climb the stairs of a housing tower at Naval Air Facility Atsugi, Japan, Sept. 11, 2014, as part of a stair climb in observance of 9/11. Terrorists hijacked four passenger aircraft Sept. 11, 2001. Two of the aircraft were deliberately crashed into the World Trade Center in New York; one was crashed into the Pentagon; the fourth crashed near Shanksville, Pa. Nearly 3,000 people died in the attacks.