160909-N-ZI635-007 WASHINGTON (Sept. 9, 2016) Attendees listen to opening remarks during an observance ceremony to commemorate the 15th anniversary of the September 11, 2001 attack on the Pentagon. The Pentagon Memorial, located on Boundary Channel Drive in Arlington, Va., commemorates the 184 lives lost at the Pentagon headquarters and on-board American Airlines Flight 77 during the terrorist attacks. (U.S. Navy photo by Mass Communication Specialist 2nd Class George M. Bell/Released)