On Sept. 11, 2001, nearly 3,000 people were killed on America's worst day of terrorism as 19 al-Qaida terrorists hijacked four passenger jetliners. Two planes smashed into New York's World Trade Center, causing the twin towers to fall; one plowed into the Pentagon; and the fourth crashed into a field in western Pennsylvania.
On Tuesday night, two glorious beams of light will pierce the New York skyline where the Twin Towers used to be in remembrance of everyone who lost their lives on that fateful morning. It's an occurrence that has become a staple on the anniversary.
Victims' families and others will gather and grieve Tuesday at ground zero, the Pentagon and near Shanksville, Pa., for the first time after the emotional turning point of last year's 10th anniversary.
President Barack Obama and first lady Michelle Obama plan to attend the Pentagon ceremony and visit wounded soldiers at Walter Reed Army Medical Center. Vice President Joe Biden and Secretary of the Interior Ken Salazar are expected to speak at the Flight 93 National Memorial near Shanksville, at the site where the hijacked United Airlines plane went down.
Secretary of Defense Leon Panetta attended a touching memorial ceremony at the Flight 93 National Memorial in Shanksville, Pa on Monday. He called the site "the final resting place of American patriots" and expressed the nation's debt to the heroes of flight 93.
Both President Barack Obama and Republican challenger Mitt Romney plan to take down their negative ads in honor of the 11th anniversary of the 9/11 terrorist attacks. Neither planned to appear at overtly political events.
Perhaps the most obvious signal that the presidential campaign is on hold is that negative ads will be taken off the air, following precedent.
Obama has scheduled a moment of silence at the White House and a trip to the Pentagon, the target of one of four planes al-Qaida hijacked 11 years ago. Romney, meanwhile, is set to address the National Guard, whose members deployed as part of the U.S. response to the attacks.
Further, for the first time, elected officials won't speak Tuesday at the Sept. 11 anniversary ceremony at ground zero. The change was made in the name of sidelining politics, but some have rapped it as a political move in itself.
Still, there will be no shortage of tributes to the victims of 9/11 on Tuesday. One memorial at Highland Memorial Park in Ocala, Florida, displays 2,741 American flags -- one for each of the attacks' victims. Another at Pepperdine University in California includes a flag from the nationality of each person killed on Sept. 11, 2001.
Even young Indian students in Amritsar, India held a candlelit vigil and offered prayers ahead of the 11th anniversary of the Sept. 11 terrorist attacks on the World Trade Center on Monday.
And while the nation will mourn on this day, we will never forget.
The Associated Press contributed to this report.