Relatives, survivors, and rescuers will attend ceremonies at the three sites.
Monday marks the 16th anniversary of the 9/11 terror attacks where almost 3,000 people were killed.
For 16 years, Flight 93's cockpit recordings served as the final, collective rallying cry from the plane's 40 passengers and crew members. Not long after, he became the first recorded victim of the terrorist attacks.
"Our country came together that day". Another passenger, Todd Beamer, was heard over an open line saying, "Are you guys ready?" Remember why it's a good idea to do these things every day. The tribute shoots two beams of light into the sky to represent the Twin Towers, destroyed in the attack.
Yet each ceremony also takes on personal touches. Trump has not provided the names of those he knew who perished in the attack, but has mentioned knowing a Catholic priest who died while serving as a chaplain to the city's fire department.
We are inviting you, our readers to share your stories from September 11, 2001. "I love you, honey". "I'm very proud to be your namesake". The horrific attack killed 2,977 people in NY.
He said that when America is united, "no force on earth can break us apart".
It preserved their heart and heroism - but also the "hateful" voices of terrorists who were intent on bringing death and destruction that day, said Patrick White, Friends of Flight 93 National Memorial president. A fourth, destined for Washington, D.C., crashed in Pennsylvania after passengers tried to overcome the hijackers, killing all those aboard.
A JNF monument in Arazim Valley near Jerusalem, called the 9/11 Living Memorial, is the only monument outside of the United States that lists the names of all the victims. "To understand - and never forget". She is making a documentary about the children who lost parents in the attacks.