Photos: Sept. 11 anniversary

People gather at one of the pools at the National September 11 Memorial following a morning commemoration ceremony for the victims of the terrorist attacks fifteen years after the day on September 11, 2016 in New York City.

Visitors at the Wall of Names at the Flight 93 National Memorial on the 15th Anniversary of the September 11th terrorist attacks, September 11, 2016 in Shanksville, PA.

Visitors view the flight path of United Flight 93 from the overlook at the Flight 93 National Memorial on the 15th Anniversary of the September 11th terrorist attacks, September 11, 2016 in Shanksville, PA.

Visitors stroll past a memorial wreath at the Wall of Names at the Flight 93 National Memorial before the 15th Anniversary of the September 11th terrorist attacks, September 11, 2016 in Shanksville, Pa.

A visitor traces the date etched in a marble slab on the Wall of Names at the Flight 93 National Memorial before the 15th Anniversary of the September 11th terrorist attacks, September 11, 2016 in Shanksville, PA.

President Barak Obama, left, shakes hands with Chairman of the Joint Chiefs Marine Corps Gen. Joseph Dunford, right, as Secretary of Defense Ashton Carter, center, looks on after delivering remarks at the Sept. 11 memorial observance ceremony at the Pentagon, Sunday, Sept. 11, 2016.

President Barack Obama listens as Secretary of Defense Ash Carter speaks during a memorial ceremony to commemorate the 15th anniversary of the 9/11 terrorist attacks, Sunday, Sept. 11, 2016, at the Pentagon in Washington.

President Barack Obama bows as a moment of silence is observed during a memorial ceremony at the Pentagon in Washington to commemorate the 15th anniversary of the 9/11 terrorist attacks, Sunday, Sept. 11, 2016.

Democratic presidential candidate Hillary Clinton waves after leaving an apartment building Sunday, Sept. 11, 2016, in New York. Clinton’s campaign said the Democratic presidential nominee left the 9/11 anniversary ceremony in New York early after feeling “overheated.” (AP Photo/Andrew Harnik)  (Andrew Harnik / AP)

A visitor pays tribute to the passengers and crew of Flight 93 at the Flight 93 National Memorial in Shanksville, Pa, on Sept. 11, 2016, as the nation marks the 15th anniversary of the Sept. 11 attacks.

A mourner holds a photo of her loved one during the 15th anniversary of the attacks of the World Trade Center at the National September 11 Memorial on Sept. 11, 2016, in New York.

A mourner holds a photo of her loved one during the 15th anniversary of the attacks of the World Trade Center at the National September 11 Memorial, Sunday, Sept. 11, 2016, in New York.

A mourner holds a photo of their loved one during the 15th anniversary of the attacks of the World Trade Center at the National September 11 Memorial, Sunday, Sept. 11, 2016, in New York.

Republican presidential candidate Donald Trump, center, attends a ceremony at the Sept. 11 memorial in New York on Sept. 11, 2016, on the 15th anniversary of the Sept. 11 attacks.

Hillary Clinton, center, accompanied by Sen. Chuck Schumer, D-N.Y., center left, Rep. Joseph Crowley, D-N.Y., second from left, and New York Mayor Bill de Blasio, center top, attends a ceremony at the Sept. 11 memorial in New York on Sept. 11, 2016.

In this U.S. Navy handout, the sun rises at the Pentagon prior to a ceremony to commemorate the 15th anniversary of the Sept. 11, 2001 terror attacks on Sept. 11, 2016. The American flag is draped over the site of impact at the Pentagon.

Mourners hold photos of their loved ones during the 15th anniversary celebration of the attacks of the World Trade Center at the National September 11 Memorial on Sept. 11, 2016, in New York.

The Tribute in Light rises above the lower Manhattan skyline Sept. 10, 2016, in New York.

A U.S. flag is draped on the side of the Pentagon on Sept. 11, 2015, where the building was stuck by a jetliner piloted by terrorists 14 years before.

Army Sgt. Edwin Morales prays during a ceremony at the World Trade Center site in New York on Sept. 11, 2015.

Paul Murdoch, architect of the Flight 93 National Memorial Visitors Center, rings a bell each time the name of one of the 40 passengers and crew of United Flight 93 is read during a Sept. 11, 2015, service at the memorial in Shanksville, Pa., as the nation marks the 14th anniversary of the Sept. 11 attacks.

President Barack Obama, first lady Michelle Obama and others pause on the South Lawn of the White House on Sept. 11, 2015, as they observe a moment of silence to mark the 14th anniversary of the 9/11 attacks.

Julia Hernandez is reflected in a photo of a relative during a ceremony at the World Trade Center site in New York on Sept. 11, 2015.

Family and friends of the 40 passengers and crew of United Flight 93 gather around a boulder that marks the crash site after a remembrance service at the Flight 93 National Memorial in Shanksville, Pa., on Sept. 11, 2015.

Visitors pause at the Wall of Names after a remembrance service at the Flight 93 National Memorial in Shanksville, Pa., on Sept. 11, 2015, as the nation marks the 14th anniversary of the Sept. 11 terrorist attacks.

Secretary of Defense Ash Carter lays a wreath during a ceremony at the Pentagon Memorial on Sept. 11, 2015.

Victims’ family members look on during a ceremony at the World Trade Center site in New York on Sept. 11, 2015, 14 years after terrorist attacks killed nearly 3,000 people in New York, Pennsylvania and Washington, D.C.

Family members of a 9/11 victim trace his name as they attend the 14th anniversary ceremony of the terrorist attacks at the 9/11 memorial in New York.

Rocco diNardo, of New York, prays while standing at the engraved name of his cousin Marisa diNardo at the edge of the South Pool during memorial observances on the 14th anniversary of the 9/11 terrorist attacks in New York.