Lt. Col. Greg Penning, assistant director of the Air, Space and Information Operations Directorate for the 601st Air & Space Operations Center, stands outside the AOC's 9/11 memorial at Tyndall Air Force Base, Fla. The memorial, which is made up of steel girders from Tower 2 of the World Trade Center, scorched limestone from the Pentagon, and chiseled segments of flagstone from a quarry near Shanksville, Pa., stands as a daily reminder to those who pass by to never forget that fateful September day. (U.S. Air Force photo/1st Lt. Jared Scott)