Defense Secretary Ash Carter attends a wreath ceremony during a memorial for the 14th anniversary of the September 11th attacks, Sept. 11, 2015, at the Pentagon.
1/9President Barack Obama, first lady Michelle Obama and others observe a moment of silence to mark the 14th anniversary of the 9/11 attacks, on the South Lawn of the White House in Washington, Sept. 11, 2015.
2/9Low clouds surround the top of the One World Trade Center tower, center left, at sunrise during the 14th anniversary of the terrorist attacks, Sept. 11, 2015.
3/9On the 14th anniversary of the attack, a U.S. flag is draped on the side of the Pentagon, Sept. 11, 2015, where the building was attacked on September 11th in 2001.
4/9Army Sgt. Edwin Morales prays during a ceremony at the World Trade Center site in New York, Sept. 11, 2015.
5/9Lanterns are carried during a candlelight memorial to the passengers and crew of United Flight 93, at the Flight 93 National Memorial in Shanksville, Pennsylvania, Sept. 10, 2015.
6/9Defense Secretary Ash Carter bows his head during a moment of silence at the Pentagon Memorial, Sept. 11, 2015, during a service on the 14th anniversary of the terrorist attacks.
7/9Chris Miller, right, and Terry Miller, center, look for their brother Robert Cromwell Miller's name on the "Empty Sky" memorial to New Jersey's victims of the 9/11 2001 terrorist attacks, as nephew James Miller, left, looks on early on Sept. 11, 2015, in
8/9An unidentified man takes photos before sunrise at the National 9/11 Pentagon Memorial, Sept. 11, 2015, on the 14th anniversary of the 911 attacks.
9/9NATO forces observe a moment of silence during a memorial ceremony on the 14th anniversary of the 9/11 terrorist attacks on the United States, at the headquarters of the International Security Assistance Force, in Kabul, Afghanistan, Sept. 11, 2015.