People walk through the Oculus at the former World Trade Center site on the 17th anniversary of the september 11 terrorist attacks.
Almost 3,000 people died in the attacks on 9/11, when worldwide terrorism hit home in a way it previously hadnt for many Americans.
In a field amid rolling hills, the 93-foot edifice was dedicated to the passengers on board who, after learning terrorists had moments before hit the World Trade Center and the Pentagon, made a decision to fight the terrorists who hijacked their jetliner.
The president and first lady Melania Trump planned to join an observance at the September 11 memorial in a field near Shanksville, Pennsylvania, where a new "Tower of Voices" was dedicated Saturday.
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Trump and his wife, Melania, traveled to the Flight 93 National Memorial from Washington and paused for a moment of reflection while overlooking the field where the plane crashed.
He said: "This field now now a message to the world: America will never submit to tyranny".
Memorials to 9/11 continue to grow at Shanksville, where a newly dedicated Tower of Voices will eventually include a wind chime for each of the 40 people killed there, and ground zero, where work is to begin soon on a pathway honoring rescue and recovery workers.
Trump received a round of applause when he suggested the best way to honour the victims was to "never flinch in the face of evil" and "do whatever it takes to keep America safe".
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"Today, we remember our beloved fallen, whose names are enshrined at this Pentagon Memorial and will forever be etched in the hearts of the American people for as long as this Nation endures", he tweeted.
Almost 3,000 people died when hijackers flew jet planes into the World Trade Center in NY and the Pentagon in Northern Virginia.
Paying tribute to the victims, he said: "Seventeen years ago, 40 incredible men and women show the whole world no force on Earth will ever conquer the American spirit". According to its official website, it also contains the "largest manmade waterfalls in the United States".
Of those he said 7,000 have "died facing down the menace of radical Islamic terrorism".
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President Trump greeted supporters with a clenched jaw and double fist pumps as he arrived at a Pennsylvania airport for a 9/11 service - prompting a social media backlash over what many said were inappropriate gestures for the solemn day.