The US President's less-than-sombre reaction was captured on Tuesday as he arrived in Pennsylvania, along with First Lady Melania Trump, on his way to pay respects to the fallen heroes of United Airlines Flight 93.
In all, almost 3,000 people were killed on 9/11 when hijackers flew airplanes into New York's World Trade Center, the Pentagon and the Pennsylvania field.
Ceremonies are also being held at New York City's 9/11 Memorial plaza on the World Trade Center site.
A minute of silence was marked at the exact times -08h46 and 09h03- where the hijacked planes came successively hit the twin towers.
The Tribute in Light is seen in the sky above Lower Manhattan area of NY from across the Hudson River on the 17th anniversary of the Sept. 11 terror attacks, Tuesday, Sept. 11, 2018, in Jersey City, N.J. "They did not sit back and let events unfold before them".
Former Pennsylvania Gov. Mark Schweiker, who was the lieutenant governor during the attack, shared his feelings of those who were on Flight 93. "It's part of what it means to be human in the 21st century, a fear for public safety", said Perez, who was 6 when his uncle, Calixto Anaya Jr., died in the 9/11 attacks.
We're talking, of course, about President Donald Trump and First Lady Melania Trump. This memorial is now a message to the arena: "The US will by no technique, ever submit to tyranny", Trump talked about as applause rang out from the audience of Flight ninety three members of the family, dignitaries and others.
They "joined the immortal ranks of American heroes", said Trump.
Americans have looked back on the September 11 terror attacks with solemn ceremonies and a presidential tribute to "the moment when America fought back".
The Shanksville ceremony will include the sounds of the Tower of Voices, a 93-foot-tall concrete and steel structure featuring a wind chime for each person on board with its own distinctive sound. Passengers and crew members phoned loved ones and learned that two planes had already struck the World Trade Center towers.
Feaver, the head of strategic planning for the National Security Council during Bush's second term, said, "I don't think we should expect this to be a soaring rhetorical moment for the president".