LEST WE FORGET: America stands united in memory of fallen heroes on 9/11 anniversary

Relatives of those who were killed remembered what remains the deadliest single attack on US soil as they gathered at the National September 11 Memorial on Tuesday

LEST WE FORGET: America stands united in memory of fallen heroes on 9/11 anniversary

New York on Tuesday honored the nearly 3,000 people killed on September 11, 2001, in a ceremony at Ground Zero, the site where hijacked Al-Qaeda planes brought down the Twin Towers.

The 17th anniversary was commemorated in fog and gentle rain by relatives of those who were killed, police officers, firefighters, and officials, who remembered what remains the deadliest single attack on US soil.

They gathered at the National September 11 Memorial and marked moments of silences at 8:46 a.m. and 9:03 a.m., the exact times that the passenger jets struck the North and South Towers.

New York Governor Andrew Cuomo, the US ambassador to the United Nations, Nikki Haley and Mayor Bill de Blasio, together with his predecessors, Michael Bloomberg, and Rudy Giuliani, were among those who attended.

"It is not a day to give speeches, it is not a day to talk about politics. It's about the heart," said Alice Greenwald, director of the 9/11 Memorial Museum.

"We need to stand together, that's the only way we can deal with that kind of pain."

In what has become an annual tradition, relatives began reading out the long list of those who were killed, saying a few words about those who died, in a ceremony that takes longer than three hours.

The New York Stock Exchange also marked a moment of silence at 9:20 a.m. and fire stations welcomed relatives of those who were killed. The department suffered a particularly heavy blow, with a total of 343 dead.

In addition to those killed on September 11, thousands of first responders, construction workers, and residents have since developed illness, many of them terminal, as a result of inhaling the toxic fumes.

Al-Qaeda hijacked a total of four planes. The third hit the Pentagon and the fourth, Flight 93, crashed in a field in Shanksville, Pennsylvania.

Here are some of the most powerful and moving images from the day:

(Source: Alex Wong/Getty Images)
(Source: Alex Wong/Getty Images)

U.S. Vice President Mike Pence speaks during a ceremony at the National 9/11 Pentagon Memorial to mark the 17th anniversary of the 9/11 terror attacks September 11, 2018, in Arlington, Virginia. The nation observed 9/11 terror attacks that killed nearly 3000 people on American soil in 2001.

(Source: Alex Wong/Getty Images)
(Source: Alex Wong/Getty Images)

Members of U.S. military forces salute during a ceremony at the National 9/11 Pentagon Memorial to mark the 17th anniversary of the 9/11 terror attacks September 11, 2018, in Arlington, Virginia.

(Source: Spencer Platt/Getty Images)
(Source: Spencer Platt/Getty Images)

People walk by the Oculus located at the World Trade Center during a morning commemoration ceremony for the victims of the terrorist attacks seventeen years after the day on September 11, 2018, in New York City.

(Source: Spencer Platt/Getty Images)
(Source: Spencer Platt/Getty Images)

A woman who lost her boyfriend in the attacks pauses across from the World Trade Center before the start of a morning commemoration ceremony for the victims of the terrorist attacks seventeen years after the day on September 11, 2018, in New York City.

(Source: Spencer Platt/Getty Images)
(Source: Spencer Platt/Getty Images)

Gary Nielson stands across from the World Trade Center site during a morning commemoration ceremony for the victims of the terrorist attacks seventeen years after the day on September 11, 2018, in New York City. Throughout the country, services are being held to remember the 2,977 people who were killed in New York, the Pentagon and in a field in rural Pennsylvania on what was one of the worst attacks on American soil in the nation's history.

(Source: Spencer Platt/Getty Images)
(Source: Spencer Platt/Getty Images)

Members of the U.S. military walk by World Trade Center site for a morning commemoration ceremony for the victims of the terrorist attacks seventeen years after the day on September 11, 2018, in New York City.

(Source: Drew Angerer/Getty Images)
(Source: Drew Angerer/Getty Images)

Army Reserve Sgt. Edwin Morales kneels in memory of his late friend Ruben Correa, a firefighter who died in the 9/11 attacks, before the start of a commemoration ceremony for the victims of the September 11 terrorist attacks at the National September 11 Memorial, September 11, 2018, in New York City.

(Source: Alex Wong/Getty Images)
(Source: Alex Wong/Getty Images)

An American flag is unfurled down the side of the Pentagon to mark the 17th anniversary of the 9/11 terror attacks September 11, 2018, in Arlington, Virginia.

(Source: Win McNamee/Getty Images)
(Source: Win McNamee/Getty Images)

A lone trumpeter plays 'Taps' as members of the White House staff observe a moment of silence on the south lawn of the White House at 8:37 A.M., the time the first tower was hit in the attacks of September 11th, on September 11, 2018, in Washington, DC.

(Source: Win McNamee/Getty Images)
(Source: Win McNamee/Getty Images)

Members of the White House staff observe a moment of silence on the south lawn of the White House at 8:37 A.M., the time the first tower was hit in the attacks of September 11th, on September 11, 2018, in Washington, DC.