U.S. Air Force Master Sgts. Jason Brown, left, and Kristopher Russ, with the 439th Air Expeditionary Advisory Squadron, perform 100-meter bear crawls during a 9/11 memorial workout Sept. 11, 2014, at Forward Operating Base Oqab, Kabul, Afghanistan. Air Force air advisers to the Afghan Air Force completed one repetition or meter of exercises for each victim of the 9/11 terrorist attacks. 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.