Americans paused on Monday to remember the Sept. 11, 2001, attacks, 22 years after extremist hijackers seized control of jetliners and crashed them into the twin towers of New York's World Trade Center and the Pentagon.
President Joe Biden was flying to Alaska to conclude a five-day trip to India and Vietnam, and was to deliver remarks in a solemn ceremony in Anchorage.
Biden's decision to hold the event in Alaska, instead of Washington or New York, was a departure from what has been presidential custom.
Vice President Kamala Harris, second gentleman Douglas Emhoff and other officials joined families of those who died on the two planes that hit the towers and on the ground at the 9/11 Memorial, which occupies the footprints of the downed building to remember the horrific day.
Across the Potomac River from Washington, Pentagon officials held the traditional event at the US military's headquarters.
The attacks killed more than 3,000 people and prompted then-President George W. Bush to launch a "global war on terror" that included a military assault on Afghanistan to find al-Qaeda leader Osama bin Laden.
Bin Laden eluded capture until he was killed in a US raid on his Pakistan compound in 2011 ordered by then-President Barack Obama.
The 9/11 attacks were the worst assault on US soil since the 1941 Japanese attack on Pearl Harbor, Hawaii, where 2,400 people were killed.
