U.S. Air Force Lt. Gen. Sid Clarke, Continental U.S. North American Aerospace Defense Command Region-1st Air Force (Air Forces Northern) commander, recalls his memories from Sept. 11, 2001, during a memorial service Sept. 11, 2011, at the 601st Air and Space Operations Center at Tyndall Air Force Base, Fla. CONR-1st AF (AFNORTH) held a ceremony to honor the memory of those who died during the worst terrorist attack on American soil. (U.S. Air Force photo by Angela Pope/Released)