ARLINGTON, VA – SEPTEMBER 11: U.S. President Barack Obama greets family members of the victims and survivors of the September 11, 2001 attack on the Pentagon during a ceremony in observance of the terrorist attacks at the Pentagon September 11, 2013 in Arlington, Virginia. Family members of the Pentagon attack victims and survivors of the attack gathered to hear from Obama and other leaders at the National 9/11 Pentagon Memorial near the place where terrorists drove a jetliner into the Department of Defense headquarters in 2001. (Photo by Chip Somodevilla/Getty Images)