The United States is marking the 14th anniversary of the September 11th terrorist attacks. U.S. officials and many other Americans attended observances Friday to remember those killed and their loved ones. Nearly 3,000 people died on September 11, 2001 when hijackers used four passenger airplanes to carry out suicide attacks in the United States. In addition to the victims, the 19 hijackers also were killed. Al-Qaida leader Osama bin Laden and his group claimed responsibility for the attacks. U.S. forces killed him in a surprise raid on his hiding place in Pakistan four years ago. Friday morning, President Barack Obama,his wife and White House workers observed a public moment of silence in Washington. They gathered on the White House grounds at 8:46. That was the exact time when a hijacked airplane struck the World Trade Center. In New York, families of the victims gathered for a ringing of bells and reading of the names of those killed in the terrorist attacks. Moments of silence were held at 8:46 and 9:03 in the morning, when a second hijacked plane also hit the World Trade Center. Near Washington, U.S. Defense Secretary Ash Carter and other officials attended an observance at the Pentagon, the home of the Defense Department. They joined in remembering those killed when a hijacked airplane hit the Pentagon, killing 184 people. Earlier Friday, a large American flag was hung down the side of the Pentagon, where the passenger jet hit. There also was a moment of silence at 10:03 a.m. That was the time when a fourth hijacked plane crashed in western Pennsylvania. All 44 people on the plane were killed. Many Americans believe the hijackers had planned to attack a target in the nation's capital. The fourth plane came down in a field in the rural community of Shanksville. Today, a new visitors center there tells the story of the 9/11 attacks. The Flight 93 National Memorial was set up to recognize the passengers and crewmembers who attacked the hijackers. Stephen Clark is with the U.S. National Park Service. It operates the visitors center and surrounding grounds. "It just amazes me that this aircraft was but 18 minutes away from hitting Washington, D.C."The field was quiet on Friday, very different from the situation 14 years ago.Gordon Felt's brother Edward was one of the passengers on United Airlines Flight 93 on September 11, 2001. "It is surreal at times. Early on, it became very evident to us very quickly that our loved ones, the events surrounding their deaths, had historical significance to our country." The last 35 minutes of Edward Felt's life, and others on the plane, are explained at the new visitors center. Relatives hope visitors to the memorial will understand the full effect of the actions of their loved ones. "They'll get a sense of who those 40 heroes were, as well as what their collective actions did to help save the Capitol building that morning."