At a morning ceremony on the 2-year-old memorial plaza at the site of the World Trade Center, relatives recited the names of the nearly 3,000 people who died when hijacked jets crashed into the twin towers and the Pentagon and near Shanksville, Pa. They also recognized the victims of the 1993 trade center bombing.
In Washington, President Barack Obama, joined by First Lady Michelle Obama, Vice President Joe Biden and wife Jill Biden, walked out to the White House's South Lawn for a moment of silence at 8:46 a.m. – the time the first plane struck the south tower in New York. Another jetliner struck the Pentagon at 9:37 a.m.
"Our hearts still ache for the futures snatched away, the lives that might have been," Obama said.
A moment of silence was also held at the U.S. Capitol.
At the site in lower Manhattan, friends and families silently held up photos of the deceased. Others wept.
"Twelve years is like 15 minutes," said Clyde Frazier Sr., whose son Clyde Frazier Jr., died in the attack and whose remains were never found. "Time stands still because you love your child, you love your son. ... Nothing changes except he's not here. It takes a toll on your body. You still look like you, but inside, you're a real wreck."
Flight 93 Paid TributeBells tolled to mark the second plane hitting the second tower and the moments when the skyscrapers fell. Near the memorial plaza, police barricades were blocking access to the site, even as life around the World Trade Center looked like any other morning, with workers rushing to their jobs and construction cranes looming over the area.
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"In a period of 22 minutes, our loved ones made history," said Gordon Felt, president of the Families of Flight 93, whose brother, Edward, was a passenger.
Outside Washington, hundreds of people observed a moment of silence in a short, simple ceremony at Arlington's Courthouse Plaza. Arlington County is home to the Pentagon, and first responders from there were among the first on the scene that day.
Weeping and RememberingIn New York, loved ones milled around the memorial site, making rubbings of names, putting flowers by the names of victims and weeping, arm-in-arm. Former Gov. George Pataki, New Jersey Gov. Chris Christie and others were in attendance.
Douglas Hamatie, whose 31-year-old cousin Robert Horohoe worked for Cantor Fitzgerald and died on 9/11, said the day should become a national holiday.
"The kids today, they know when the next iPhone's coming out, and they know when the next Justin Bieber concert is, but they don't know enough about 9/11. So let's change that, please," he said, to applause from the crowd.
Around the world, thousands of volunteers have pledged to do good deeds, honoring an anniversary that was designated a National Day of Service and Remembrance in 2009.