NEW YORK (AP) — Americans commemorated 9/11 on Friday as another national crisis, the coronavirus, reconfigured ceremonies and as a presidential campaign carved a path through the memorials.

In New York, victims' relatives gathered Friday morning for split-screen remembrances at the World Trade Center's Sept. 11 memorial plaza and on a nearby corner, set up by separate organizations that differed on balancing tradition with virus safety.

Standing on the plaza, with its serene waterfall pools and groves of trees, Jin Hee Cho said she couldn't erase the memory of the death of her younger sister, Kyung, in the 2001 terrorist attack that destroyed the trade center's twin towers.

"It's just hard to delete that in my mind. I understand there's all this, and I understand now that we have even COVID," said Cho, 55. "But I only feel the loss, the devastating loss of my flesh-and-blood sister."

Around the country, some communities canceled 9/11 ceremonies, while others went ahead, sometimes with modifications. The Pentagon's observance was so restricted that not even victims' families could attend, though small groups could visit its memorial later in the day.

On an anniversary that fell less than two months before the presidential election, President Donald Trump and Democratic challenger Joe Biden both headed for the Flight 93 National Memorial in the election battleground state of Pennsylvania — at different times of day.

Biden also attended the ceremony at Ground Zero in New York, exchanging a pandemic-conscious elbow bump with Vice President Mike Pence before the observance began.

In short, the 19th anniversary of the deadliest terror attack on U.S. soil was a complicated occasion in a maelstrom of a year, as the U.S. grapples with a pandemic, searches its soul over racial injustice and prepares to choose a leader to chart a path forward.

Still, families say it's important for the nation to pause and remember the hijacked-plane attacks that killed nearly 3,000 people at the trade center, at the Pentagon outside Washington and in a field near Shanksville, Pa., on Sept. 11, 2001 — shaping American policy, perceptions of safety, and daily life in places from airports to office buildings.

"People could say, 'Oh, 19 years.' But I'll always be doing something this day. It's history," said Annemarie D'Emic, who lost her brother Charles Heeran, a stock trader. She went to the alternative ceremony in New York, which kept up the longstanding tradition of in-person readers.

Speaking at the Pennsylvania memorial, Trump recalled how the plane's crew and passengers tried to storm the cockpit as the hijackers as headed for Washington.

"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.

Biden visited the memorial later Friday, laid a wreath and greeted relatives of victims including First Officer LeRoy Homer. Biden expressed his respect for those aboard Flight 93, saying sacrifices like theirs "mark the character of a country."

"This is a country that never, never, never, never, never, never gives up," he said.

At the Sept. 11 memorial in New York hours earlier, Biden offered condolences to victims' relatives including Amanda Barreto, 27, and 90-year-old Maria Fisher, empathizing with their loss of loved ones. Biden's first wife and their daughter died in a car crash, and his son Beau died of brain cancer.

Biden didn't speak at that ceremony, which customarily doesn't let politicians make remarks.

Pence went on to the separate ceremony, organized by the Stephen Siller Tunnel to Towers Foundation, where he read the Bible's 23rd Psalm. His wife, Karen, read a passage from the Book of Ecclesiastes.

"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 audience of hundreds.

Formed in honor of a firefighter killed on 9/11, the foundation felt in-person readers were crucial to the ceremony's emotional impact and could recite names while keeping a safe distance. By contrast, recorded names emanated from speakers placed around the memorial plaza. Leaders said they wanted to keep readers and listeners from clustering at a stage.

As in past years on the plaza, many readers at the alternative ceremony added poignant tributes to their loved ones' character and heroism, urged the nation not to forget the attacks and recounted missed family milestones: "How I wish you could walk me down the aisle in just three weeks," Kaitlyn Strada said of her father, Thomas, a bond broker.

One reader thanked essential workers for helping New York City endure the pandemic, which has killed at least 24,000 people in the city and over 190,000 nationwide. Another reader, Catherine Hernandez, said she became a police officer to honor her family's loss.

Other victims' relatives, however, weren't bothered by the switch to a recording at the Ground Zero ceremony, which also drew hundreds.

"I think it should evolve. It can't just stay the same forever," said Frank Dominguez, who lost his brother, Police Officer Jerome Dominguez.

The Sept. 11 memorial and the Tunnel to Towers foundation also tussled over the Tribute in Light, a pair of powerful beams that shine into the night sky near the trade center, evoking the twin towers. The 9/11 memorial initially canceled the display, citing virus safety concerns for the installation crew.

After the foundation vowed to put up the lights instead, the memorial changed course with help from its chairman, former Mayor Mike Bloomberg, and Gov. Andrew Cuomo. The lights again went on at dusk Friday.

Tunnel to Towers, meanwhile, arranged to display single beams for the first time at the Shanksville memorial and the Pentagon.

The anniversary has become a day for volunteering, with the 9/11 National Day of Service and Remembrance organization encouraging people this year to make donations or take other actions from home because of the pandemic.

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Contributing to this report were Associated Press journalists Alexandra Jaffe and Ted Shaffrey in New York, Darlene Superville in Shanksville, Pa., and Mark Scolforo in Harrisburg, Pa.