The ceremony is happening near the memorial for Flight 93, one of the 4 airliners that was hijacked by Al-Quada terrorists, but crashed before it could reach its target. "America will never, ever submit to tyranny", Trump said, noting that almost 5.5 million Americans have joined the U.S. military since 9/11.
Trump has also said he lost "hundreds of friends" in the attack on New York City.
"This field is now a monument to American defiance".
They "joined the immortal ranks of American heroes", he said. The 40-odd passengers and crew attempted to take back control of the plane from the hijackers when they learned of the ongoing terror attacks at the World Trade Center in NY and at the Pentagon.
How hard is it to write a thoughtful message to the families of those lost in the attack, thank the first responders, encourage America, or at the very very least, not pump your fists?
It is believed hijackers planned to aim the aircraft at the US Congress or White House when it crashed, killing all 40 people onboard.
It was deadliest foreign attack ever on United States soil, killing 2,996 people.
It will serve as a way to honor those who became sick or died from exposure to toxins released when the Trade Centers twin towers collapsed.
Cantona: Guardiola should be Manchester United manager
United have endured a mixed start to the 2018-19 Premier League campaign, with six points from their first four games and defeats against Tottenham and Brighton.
He said the site marks the "moment when America fought back", and said the september 11 anniversary recalls the day "a band of fearless patriots turned the tide on our nation's enemies and joined the immortal ranks of American heroes". America's future is written by our heroes.
He also praised former New York City mayor Rudy Giuliani, who now serves as his lead attorney handling Russian Federation matters.
Others criticized the tone of a tweet the president sent out on his way to the memorial event, which read, "17 years since September 11th!"
And in Washington, Vice President Mike Pence spoke during the memorial observance at the Pentagon, where 125 people were killed when a jet was flown into the building.
Architect Paul Murdoch said he wanted visitors the crash site to have an emotional reaction when they come to the place where the flight slammed into earth after passengers and crew attacked the terrorists.
Trump uses "Make America Great Again" as a slogan.
"Even though I never met you, I'll never forget you", Isabella Del Corral said of her grandfather, Joseph Piskadlo.