Americans mark the 24th anniversary of the 9/11 attacks with emotional ceremonies

"Even 24 years later, it's heart-wrenching," said Jennifer Nilsen, who wore a T-shirt emblazoned with an image of her husband, Troy Nilsen, as she attended the commemoration at ground zero in lower Manhattan. "It feels the same way every year."

Michelle Pizzo, wearing a shirt with the image of her late husband, Jason DeFazio, said she hoped more people could take a minute to reflect on the day.

"Younger kids don't realize that you have to remember," she said.

Emma Williamson, 20, of Massachusetts, made a point to travel from her college uptown to stand near ground zero, where two memorial pools ringed by waterfalls and parapets inscribed with the names of the dead mark the spots where the twin towers once stood.

"I wasn't born when it happened, but it was really an important day in America," she said. "It's kind of the last time we all stuck together, and that matters."

The reading of names and moments of silence

The 9/11 anniversary, often promoted as a day of national unity, came during a time of increased politician tension.

The assassination of conservative activist Charlie Kirk at a Utah college a day earlier prompted additional security measures at ground zero, where FBI Director Kash Patel was among the dignitaries in attendance.

Vice President JD Vance and his wife, second lady Usha Vance, had planned to attend but instead are set to visit with Kirk's family on Thursday in Salt Lake City, according to a person familiar with Vance's plans, but not authorized to speak about them publicly.

Many in the crowd at ground zero held up photos of lost loved ones as a moment of silence marked the exact time when the first hijacked plane struck the iconic twin towers.

Loved ones then read aloud the names of the victims, with many giving personal remembrances, well wishes and updates on their lives.

Zoe Doyle, daughter of Frank Joseph Doyle, said her family created a nonprofit in his honor that's built schools in South Africa and is feeding and educating thousands of children.

Manuel DaMota Jr. said he remembers his father and namesake, Manuel DaMota, not just with grief, but with gratitude for the example he set.

"In a world filled with division and conflict, I do my best to honor my father by choosing connection, empathy and hope," he said.

Melissa Pullis, whose husband Edward Pullis died in the towers, said this year is more difficult than others because two of the couple's three children are getting married.

"You can't walk your princess down the aisle," she said through tears. "You are missed every day. We will always say your name, and we will always fight for justice."

Ceremonies in Virginia and Pennsylvania honor victims

At the Pentagon in Virginia, the 184 service members and civilians killed when hijackers steered a jetliner into the headquarters of the U.S. military were honored in a ceremony attended by President Donald Trump and first lady Melania Trump.

The president, in his remarks, recounted moments from that day, including snippets of conversations from passengers who were aboard the hijacked airplanes.

"Today, as one nation, we renew our sacred vow that we will never forget Sept. 11, 2001," Trump said during the observance, which took place in an internal courtyard of the building rather than its traditional location outside its walls near the building's 9/11 memorial.

"The enemy will always fail," he added. "We defy the fear, endure the flames."

The president, who was expected to attend a New York Yankees game in the Bronx on Thursday evening, also announced Kirk would be posthumously awarded the Presidential Medal of Freedom, calling him a "giant of his generation" and a "champion of liberty."

And in a rural field near Shanksville, Pennsylvania, a ceremony attended by Veterans Affairs Secretary Doug Collins honored the victims of Flight 93, the hijacked plane that crashed after crew members and passengers tried to storm the cockpit.

Elsewhere, people marked the anniversary with service projects and charitable works as part of a national day of service. Volunteers took part in food and clothing drives, park and neighborhood cleanups, blood banks and other community events.

Reverberations from attacks persist

In all, the attacks by al-Qaida militants killed 2,977 people, including many financial workers at the World Trade Center and firefighters and police officers who had rushed to the burning buildings trying to save lives.

The attacks reverberated globally, altering the course of U.S. foreign and domestic policy. It led to the " Global War on Terrorism " and the U.S.-led invasions of Afghanistan and Iraq and related conflicts that killed hundreds of thousands of civilians and troops.

The U.S. government has also spent billions of dollars providing health care and compensation to tens of thousands of people who were exposed to the toxic dust that billowed over parts of Manhattan when the twin towers collapsed.

While the hijackers died in the attacks, federal officials have struggled to conclude the long-running legal case against the man accused of masterminding the plot, Khalid Sheikh Mohammed. The former al-Qaida leader was arrested in 2003, but has never received a trial.

The Trump administration has also acknowledged its considering ways to take control of the ground zero memorial plaza and its underground museum, which are run by a public charity.