President Barack Obama pauses for a moment of silence after laying a wreath at the Pentagon Memorial, Sept. 11, 2011, with First Lady Michelle Obama, Defense Secretary Leon E. Panetta and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, to honor the 184 people killed when American Airlines Flight 77 crashed into the Pentagon during a terrorist attack 10 years ago. DOD photo by Navy Petty Officer 1st Class Chad J. McNeeley