Twenty years after hijacked airliners smashed into New York City’s World Trade Center and the Pentagon outside Washington, Americans came together on Saturday to honour the nearly 3,000 lives lost on September 11, 2001, and reflect on how the attacks have shaped the country’s view of the world and itself.

With President Joe Biden on hand, the ceremony at the September 11 Memorial in lower Manhattan began with a moment of silence at 8.46am EDT (1246 GMT), the exact time the first of two planes flew into the World Trade Center’s twin towers.

Mike Low, whose daughter was a flight attendant on the airliner that struck the North Tower described the “unbearable sorrow” experienced by his family over the past 20 years. “As we recite the names of those we lost my memory goes back to that terrible day when it felt like an evil specter had descended on our world, but it was also a time when many people acted above and beyond the ordinary,” he said.

Relatives then began to read aloud the names of 2,977 victims to the thousands who had gathered on the cool, clear morning, among them former President Barack Obama and Hillary Clinton, a junior senator at the time of the attacks.

After ground zero, Biden will visit the Pentagon in Arlington, Virginia, where a third airliner crashed; and Shanksville, Pennsylvania, where Flight 93 was downed after passengers tried to regain control of the hijacked plane.

The remembrances have become an annual tradition but Saturday has special significance, coming 20 years after the morning that many view as a turning point in US history, a day that gave Americans a sense of vulnerability that has deeply influenced the country’s political life since then.

In a painful reminder of those changes, only weeks ago US and allied forces completed a chaotic withdrawal from the war the US started in Afghanistan in retaliation for the attacks — which became the longest war in US history.

Clifford Chanin, executive vice-president at the National September 11 Memorial & Museum built at the site of the World Trade Center attack, said the two-decade milestone would serve as a “moment of high emotion” for the country, a time to consider “where we’ve been and where we are headed.”