An American flag was unfurled at sunrise over the Pentagon on Friday as the United States marked 25 years since the September 11 attacks, which killed nearly 3,000 people.
The ceremony in Arlington, Virginia, honoured the 184 people who died when American Airlines Flight 77 was hijacked and crashed into the military headquarters on September 11, 2001.
President Donald Trump was due to attend a commemorative service at the Pentagon, marking the second consecutive year he has observed the anniversary at the site rather than at Ground Zero in New York.
The attack struck the building at 9.37am. The Pentagon memorial, established beside the impact site, contains 184 memorial units bearing the names of those killed.
Vice-President JD Vance was expected to attend the main ceremony in New York, while administration officials were due to take part in commemorations at the Flight 93 site in Shanksville, Pennsylvania.
Earlier this week, Mr Trump joined first responders, Gold Star families and the Tunnel to Towers Foundation at the Ellipse in Washington for a Steel Across America event.
The gathering featured a 21ft steel beam recovered from the South Tower of the World Trade Centre. Weighing almost 17,000lb, it has travelled through 21 states as part of a nationwide memorial tour before returning to New York for the anniversary.
The Pentagon ceremony formed part of a day of memorial services, moments of silence and tributes across the country, as families and survivors remembered those killed in the attacks and the first responders who went to the scenes.
