Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. US Marks September 11th Anniversary by VOA News The United States is marking the 15th anniversary of the September 11th terrorist attacks, when al-Qaida terrorists hijacked planes and flew them into the World Trade Center in New York and the Pentagon near Washington. Another plane crashed in rural Pennsylvania. President Barack Obama observed a moment of silence at the White House Sunday at 8:46 a.m., when the first of the four hijacked planes slammed into the World Trade Center, before speaking at a ceremony at the Pentagon honoring those killed in the attacks. Victims killed in the attack on the World Trade Center will be remembered in New York, where the country's leading 2016 presidential candidates, Democrat Hillary Clinton and Republican Donald Trump, are paying their respects at Ground Zero but halting their political campaigns for the day. As they have been in past 9/11 commemorations in New York, the names of the 2,983 killed that horrifying day will be read slowly by their relatives as music plays in the background. As daylight ends Sunday in New York, spotlights will project two giant beams of light into the sky to represent the fallen twin towers of the World Trade Center. "Fifteen years ago, a September day that began like any other became one of the darkest in our nation's history," Obama said Saturday in his weekly address. The president said nearly "3,000 innocent lives were lost" that September day "from all walks of life, all races and religions, all colors and creeds, from across America and around the world." It was the worst attack on U.S. soil since Pearl Harbor was bombed in 1941 at the start of World War Two. Nineteen hijackers, 15 of them from Saudi Arabia, were killed in the attacks, which led directly to the U.S. war in Afghanistan, where al-Qaida trained attackers against the United States, and indirectly to the war in Iraq. The U.S. still has thousands of forces in Iraq and Afghanistan even as it has ended large-scale combat operations. Obama said a lot has changed over the past 15 years, but "it's also important to remember what has not changed - the core values that define us as Americans. The resilience that sustains us . . . terrorists will never be able to defeat the United States." Writing on Twitter Sunday, Secretary of State John Kerry said, "On 9/11, we remember those we lost, those who tried to save them. We honor them by pursuing peace, security, justice worldwide." Near Shanksville in western Pennsylvania Sunday, the Flight 93 National Memorial stands in memory of the passengers and crew members who carried out a sustained assault against the hijackers for control of the plane 15 years ago. A September 11 Museum has been erected on the New York site where the World Trade Center once stood, housing artifacts and photographs connected to the attack. At the Pentagon, the 184 people who died on September 11, 2001 are honored with 184 benches over pools of water.