Fourteen years ago Friday, terrorists hijacked four passenger planes and smashed two into New York's World Trade Center.
A third jetliner rammed into the Pentagon outside Washington while a fourth one crash-landed on an empty field in Pennsylvania.
People, buildings and planes fell from the sky. Terrified strangers became friends as Americans united on a day that changed the world forever.
On Friday, a resilient nation looked to the future while honoring the past.
Here are the main events that paid tribute to the many lives lost on September 11, 2001:
At the site of the World Trade Center, where most of the victims were
, bagpipers and drummers provided solemn tunes to accompany an hours-long ceremony.
Relatives of those who died stood at podiums at the National September 11 Memorial plaza, reading the names of victims. Each speaker read a block of names before ending with their own loved one, adding a few words of remembrance for their lost sibling, child, parent or cousin.
Moments of silence were observed at the specific times when the planes struck and the buildings fell.
The first plane hit the north tower at 8:46 a.m. The second one struck at 9:03 a.m.
In this attack, 2,753 people died when terrorists intentionally crashed American Airlines Flight 11 and United Airlines Flight 175 into the north and south towers, respectively.
More than 300 firefighters were among those who perished in the attacks and the collapse of the towers. Dozens more were police officers.
Hundreds of miles away, a passenger jetliner crashed near Shanksville, Pennsylvania, at 10:03 a.m.
Crowds there marked a moment of silence at that exact time and read out the names of the victims.
Forty passengers and crew members aboard United Airlines Flight 93 died when the plane crashed into the field. It is believed that the hijackers crashed the plane in that location, rather than their unknown target, after passengers and the crew attempted to retake control.
At the Pentagon, 184 people died when hijacked American Airlines Flight 77 crashed into the building at 9:37 a.m.
Shortly after 9:30 a.m. Friday, a ceremony
began at the Pentagon Memorial, attended by relatives of the victims. It included wreath laying and remarks by Defense Secretary Ash Carter.
At the White House, the President and first lady Michelle Obama stepped onto the South Lawn for a minute of silence at 8:46 a.m. -- the time the first jet hit the World Trade Center.
Obama made no comment at that observance, but he later visited Fort Meade in Maryland
, where he talked with troops and expressed his appreciation.
"The President very much values face time with troops -- listening, asking and answering questions, and he looks forward to taking time on the anniversary of 9/11 to engage directly with service members," Pentagon spokesman Peter Cook said.
Outside the Justice Department headquarters in Washington, a crew planted a pear tree -- an offspring of one at the World Trade Center plaza that survived the buildings' fall. The original tree stands at the 9/11 memorial in New York.
The tree is a reminder that "we can endure, we can prevail, and we, too, can bloom again," Attorney General Loretta Lynch said at the ceremony.