The President delivered a speech commemorating the airplane passengers who are thought to have charged the cockpit to stop the attackers.

Meanwhile, the ceremonies are also being held at New York City's 9/11 Memorial plaza on the World Trade Center site.

It will be recalled that the 9/11attack is the  deadliest foreign attack ever on US soil, killing like 3,000 people.

"America's future is not written by our enemies. America's future is written by our heroes," Mr Trump said in Shanksville on Tuesday.

"As long as this monument stands, as long as this memorial endures, brave patriots will rise up in America's hours of need and they, too, will fight back."

The president spoke at the newly inaugurated Tower of Voices memorial, a 93ft (28m) tall structure with 40 wind chimes.