Defense Secretary Ash Carter, right, bows his head during a wreath ceremony at a memorial for the 14th anniversary of the September 11th attack at the Pentagon. (Jacquelyn Martin)
Former Mayor of New York City Rudy Giuliani attends a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
From left, former mayors of New York, Rudy Giuliani, Michael Bloomberg and Mayor Bill de Blasio attend a ceremony at the World Trade Center site. (Bryan R. Smith)
New York Gov. Andrew Cuomo and former Gov. George Pataki attend a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
A visitor pauses at the Wall of Names at sunrise before a Service of Remembrance at the Flight 93 National Memorial in Shanksville, Pa, Friday, Sept. 11, 2015. (Gene J. Puskar)
A National Park Ranger's shadow falls on the Wall of Names at sunrise before a Service of Remembrance at the Flight 93 National Memorial in Shanksville, Pa. (Gene J. Puskar)
Visitors touch the names of the victims of the Sept. 11 terror attacks at the South Pool of the National September 11 Memorial on Friday, Sept. 11, 2015 in New York. (Bryan R. Smith)
Army Sgt. Edwin Morales prays during a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
A visitor pauses on the observation deck of the Flight 93 National Memorial Visitors Center in Shanksville, Pa, Friday, Sept. 11, 2015. (Gene J. Puskar)
A flag is placed along the South Pool prior to a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
Retired New York City firefighter Joseph McCormick visits the South Pool prior to a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
Retired New York City firefighter Joseph McCormick visits the South Pool prior to a ceremony at the World Trade Center site in New York on Friday, Sept. 11, 2015. (Bryan R. Smith)
At the Pentagon Memorial a K-9 officer pauses as the flag is draped on the side of the Pentagon Friday Sept. 11, 2015, in Washington. (AP Photo/Jacquelyn Martin) (Jacquelyn Martin)
A U.S. flag is draped on the side of the Pentagon, Friday, Sept. 11, 2015. (AP Photo/Jacquelyn Martin) (Jacquelyn Martin)
Two Emergency Medical Technicians pause to look at the names on the "Empty Sky" memorial to New Jersey's victims of the Sept. 11, 2001 terrorist attacks in Jersey City, N.J. (Mel Evans)
The sun rises, as One World Trade Center, center left, stands on the 14th anniversary of the Sept. 11, 2001 terrorist attacks. (Mel Evans)
A runner stops to take a photograph of names on the "Empty Sky" memorial to New Jersey's victims of the Sept. 11, 2001 terrorist attacks in Jersey City, N.J. (AP Photo/Mel Evans) (Mel Evans)
A group holds flags as they prepare to run at the "Empty Sky" memorial to New Jersey's victims of the Sept. 11, 2001 terrorist attacks. (Mel Evans)
Terry Miller, right, and Chris Miller, center, look for their brother's name on the "Empty Sky" memorial in New Jersey, as nephew James Miller looks on. (Mel Evans)