Shanksville, Pennsylvania: President Donald Trump has remembered the "band of brave patriots" aboard a September 11 flight that crashed in Pennsylvania, praising passengers and crew members who resisted hijackers and sent a message that the nation would "never, ever submit to tyranny".

Trump honoured those killed 17 years ago at a rural field where the fourth airliner of the day crashed after those aboard realised what was happening and several passengers tried to storm the cockpit. The President praised those who "took control of their destiny and changed the course of history".

"A piece of America's heart is buried on these grounds, but in its place has grown a new resolve to live our lives with the same grace and courage as the heroes of Flight 93," Trump said. "This field is now a monument to American defiance. This memorial is now a message to the world: America will never, ever submit to tyranny."

Trump listened as the names of the 40 victims were read aloud, followed by the tolling of bells. He was joined in remembrances by his wife, first lady Melania Trump, Pennsylvania Governor Tom Wolf and former governor Mark Schweiker, who was the state's lieutenant governor on September 11, 2001.

Nearly 3,000 people died that day when other airplanes were flown into New York's World Trade Centre and the Pentagon in an attack planned by al-Qaeda leader Osama bin Laden. Bin Laden was killed in May 2011 during a US military operation ordered by President Barack Obama.