Americans have commemorated 9/11 as the coronavirus pandemic reconfigured anniversary ceremonies and a presidential campaign carved a path through the observances.
In New York, victims’ relatives gathered for split-screen remembrances, one at the September 11 memorial plaza at the World Trade Centre and another on a nearby corner.
A foundation that honours the sacrifice paid by firefighters during the disaster objected to the memorial’s decision to forgo a longstanding tradition of having relatives read the names of the dead.
The Tunnel to Towers Foundation arranged its own, simultaneous ceremony, saying there was no reason that people could not recite names while keeping a safe distance.
Reverence for the dead “requires that we read these names out loud, in person, every year”, said foundation chairman Frank Siller, whose brother Stephen was a firefighter.
Memorial leaders said they made the change as a coronavirus-safety precaution on the 19th anniversary of the deadliest terror attack on US soil.
Kathy Swift arrived early at the alternative ceremony a few blocks away, wearing a T-shirt honouring her killed brother, Thomas Swift, who worked in finance.
“We still have to remember,” said Ms Swift, 61. “The whole country’s going downhill, it’s one thing after another, and now with the Covid. I’m glad they’re still having this, though.”
President Donald Trump addressed a ceremony at the Flight 93 National Memorial near Shanksville, Pennsylvania.
“The heroes of Flight 93 are an everlasting reminder that no matter the danger, no matter the threat, no matter the odds, America will always rise up, stand tall, and fight back,” the Republican president said.
Former vice president Joe Biden laid a wreath under First Officer LeRoy Homer’s name at the Flight 93 memorial, before going to greet some of Mr Homer’s family members with elbow bumps.
Mr Biden went on to greet another family of a Flight 93 victim, as well as a young bagpipe player, whom he asked about her college plans.
He spoke to a few people gathered about his respect for the passengers on the flight that sacrificed themselves to help bring it down, and said sacrifices like theirs “mark the character of a country”.
“This is a country that never, never, never, never, never, never gives up,” he said.
Mr Biden then visited the Shanksville Volunteer Fire Department, where he delivered a Bundt cake and pastries to firefighters.
Earlier, he attended the observance at the 9/11 memorial in New York, exchanging an elbow bump with vice president Mike Pence before the ceremony began with the usual tolling of a bell.
Mr Biden offered condolences to a woman he spotted crying in the crowd of hundreds, Amanda Barreto, who lost her aunt and godmother in the attacks.
Ms Barreto, 27, said Mr Biden “wanted to let me know to keep the faith” and “wanted me to say strong”, telling her he understood what it meant to lose a loved one.
His first wife and their daughter died in a 1972 car crash, and his son Beau died of brain cancer in 2015.
Mr Biden did not speak at the ceremony, which has a longstanding custom of not allowing politicians to make remarks.
Mr Pence went on to the Tunnel to Towers Foundation ceremony, where he read from the Bible.
“For the families of the lost and friends they left behind, I pray these ancient words will comfort your heart and others,” said the vice president, drawing applause from the crowd of hundreds.
The anniversary of 9/11 is a complicated occasion this year, as the US grapples with a health crisis, searches its soul over racial injustice and prepares to choose a leader to chart a path forward.
Still, families say it is important for the nation to pause and remember the hijacked-plane attacks that killed nearly 3,000 people at the trade centre, at the Pentagon in Washington and near Shanksville on September 11 2001.
Around the country, some communities cancelled 9/11 commemorations because of the pandemic, while others went ahead, sometimes with modifications.
The Pentagon’s observance was so restricted that not even victims’ families could attend, though small groups can visit the memorial there later in the day.
At the New York memorial, thousands were still invited.