Airmen from the 436th Civil Engineer Squadron and 436th Security Forces Squadron raise the flag in honor of the victims of 9/11, on Sept. 11, 2013, at Dover Air Force Base, Del. The memorial incorporates two pieces of steel from World Trade Center tower one, a rock from the United Airlines Flight 93 crash site and a block from the damaged portion of the Pentagon. (U.S. Air Force photo/David S. Tucker)