The United States witnessed its deadliest terror attack on Sept. 11, 2001, which resulted in the deaths of nearly 3,000 people. Nineteen suicide bombers belonging to the terrorist outfit al-Qaida hijacked four passenger jets and crashed them into the Twin Towers in New York, the Pentagon in Washington and a field in Shanksville, Pennsylvania.

This Sunday marks the 15th anniversary of the first foreign attack on U.S. soil in nearly two centuries.

Sep 11 attacks Pedestrians react to the World Trade Center collapse in New York City, Sep. 11, 2001. Photo: REUTERS/STRINGER

Several people, including the families of those who lost loved ones in the attacks, will gather at the World Trade Center site Sunday to pay tribute to the lives lost. The family members will begin the annual reading of the names of the 2,977 people who died in New York, Arlington and Pennsylvania and the six people who died in the 1993 World Trade Center bombing.

The reading will pause six times to mark the moments when the first plane struck the North Tower at 8:46 a.m. EDT, when the second plane crashed into the South Tower at 9:03 a.m. EDT, when Flight 77 struck the Pentagon at 9:37 a.m. EDT, when the South Tower fell at 9:59 a.m. EDT, when Flight 95 crashed in Pennsylvania at 10:03 a.m. EDT and finally at 10:28 a.m. EDT when the North Tower fell.

At 8:46 a.m. EDT, the first pause, houses of worship across New York City will toll their bells as the crowd observes the annual moment of silence.

The number of people that attend the ceremony has fallen over the years but many believe that this year holding special significance and the day falling during a weekend might draw more numbers.

“Parents of the deceased are getting older, younger people usually can’t make it because of work obligations,” Tom Acquaviva told USA Today. Acquaviva’s 29-year-old son, Paul, died on 9/11. “But I hope this year you will see a lot more people than previous years.”

He added that he thinks of his son daily but there was something about the anniversary of the attacks. “My wife and I lost everything. You carry on, but you don’t move on,” he said.

9/11 memorial Albert Biatta, of Queens, New York, prays while standing in front of the inscribed name of his uncle Antoine Biatta at the edge of the North Pool during memorial observances held at the site of the World Trade Center in New York, Sep. 11, 2014. Photo: REUTERS/JUSTIN LANE/POOL

The 15th anniversary of the attacks falls in the midst of the heated presidential elections. Both former Secretary of State Hillary Clinton who was a senator from New York during the attacks and New York native Donald Trump are scheduled to attend the memorial.

Former President George W Bush who was in office during the attacks will be skipping the memorials both in Washington and New York. His office reportedly said that the former president will be attending church in Dallas and then proceed to the Dallas Cowboys home opener against the New York Giants. There, Bush will participate in the ceremonial coin toss with two New York police officers who were at ground zero when the attacks occurred.

President Obama will observe a moment’s silence at the White House at 8:46 a.m. EDT before heading to the Pentagon where he will deliver an address during the memorial ceremony.

In his weekly radio and internet address Saturday, Obama lauded the bravery of survivors, of emergency personnel who rushed to help victims and all others who have worked on keeping the country safe since the attacks.

“In the face of terrorism, how we respond matters ... We cannot give in to those who would divide us. We cannot react in ways that erode the fabric of our society. Americans will never give in to fear,” the president reportedly said. “We’re still the America of heroes who ran into harm’s way, of ordinary folks who took down the hijackers, of families who turned their pain into hope.”

The president also reiterated the country’s commitment in fighting against terrorist outfits like the al-Qaida and the Islamic State group. “We will destroy them. And we'll keep doing everything in our power to protect our homeland,” he added.

On Saturday, 20 people pedaled along the newly opened September 11th National Memorial Trail. Only a 21-mile section of the cycle trail has been opened so far. The entire trail is 1,300 miles long and connects all three 9/11 memorials. 

The purpose of the trail is to honor the heroes who lost their lives in the attack, David Brickley, president and CEO of the Sept. 11th National Memorial Trail said.

“We’re going to be stronger, more resilient. That’s what this is about,” he said at the opening. “It took a lot of perseverance. It will also contribute to the economic vitality of the area.”