The U.S. prepares to mark the 15th anniversary of the 9/11 attacks

The United States prepares to commemorate the 15th anniversary of the September 11, 2001 attacks on the World Trade Center and the Pentagon.

NEW YORK, NEW YORK, UNITED STATES (NBC) – Thousands of people will gather in New York City, Washington D.C and Shanksville, Pennsylvania on Sunday (September 11) to remember the nearly 3,000 people killed when hijacked jetliners crashed into the World Trade Center, the Pentagon and a field in Pennsylvania on September 11, 2001.

In New York City, a ceremony will take place at the 9/11 Memorial.

Fifteen years on, mourners will gather as they have every year since the attack, for the annual reading of victims’ names from both the 1993 and 2001 attacks on the World Trade Center.

They will also observe a citywide moment of silence at 8:46 a.m. EDT (1246GMT), the time American Airlines Flight 11 crashed into the North Tower, with a second pause at 9:03 a.m. when United Airlines Flight 175 struck the South Tower.

Further moments of silence will be observed at 9:37 a.m., when American Airlines Flight 77 hit the Pentagon; at 9:59 a.m. when the South Tower fell; at 10:03 a.m. when United Flight 93 hit the ground near Shanksville, Pennsylvania; and at 10:28 a.m., when the North Tower collapsed.

Osama bin Laden and al Qaeda claimed responsibility for the suicide attacks and a U.S.-led war in Afghanistan followed.

U.S. forces killed bin Laden in May 2011 in a surprise raid on his hideout in Abbottabad, Pakistan, ending a nearly 10-year hunt for the al Qaeda leader.