Gallery: New York remembers 9/11

The World Trade Center south tower (L) bursts into flames after being struck by hijacked United Airlines Flight 175, as the north tower burns following an earlier attack. FILE PHOTO: Sean Adair/Reuters

The World Trade Center south tower (L) bursts into flames after being struck by hijacked United Airlines Flight 175, as the north tower burns following an earlier attack. FILE PHOTO: Sean Adair/Reuters

In this Sept. 11, 2001 file photo, people run from a collapsing World Trade Center tower in New York. Photo: Suzanne Plunkett/AP

This Sept. 8, 2008 file photo shows the early stages of reconstruction starting at the World Trade Center site in New York. Photo: Mark Lennihan/AP

The Tribute in Light is illuminated on the skyline of lower Manhattan during events marking the 13th anniversary of the 9/11 attacks on the World Trade Center in New York, September 10, 2014. Until a few months ago, the part of New York City where crowds will gather on Thursday morning to mark the 13th anniversary of the September 11 attacks on the U.S. had been mostly fenced off to the public. This year, for perhaps the first time since the attacks, a sense of normalcy and openness has taken root in the city blocks where two airliners hijacked by militants from al Qaeda crashed into the World Trade Center's twin towers. REUTERS/Eduardo Munoz (UNITED STATES - Tags: POLITICS ANNIVERSARY TPX IMAGES OF THE DAY DISASTER)

The Tribute in Light rises behind buildings adjacent to the 1 World Trade Center. Photo: Mark Lennihan/AP

A man walks through the 9/11 Empty Sky memorial ahead of the 13th anniversary of the 9/11 attacks on the World Trade Center, in Jersey City. Photo: Eduardo Munoz/Reuters

A woman watches the Tribute in Light illuminated on the skyline of lower Manhattan during events marking the 13th anniversary of the 9/11 attacks on the World Trade Center. Photo: Eduardo Munoz/Reuters

A necklace with a cross is seen hanging from a 9/11 Memorial art piece outside a firehouse near the World Trade Center site in New York. Photo: Shannon Stapleton/Reuters

The Tribute in Light rises behind buildings adjacent to the 1 World Trade Center and a reflecting pool at the National September 11 Memorial. Photo: Mark Lennihan/AP