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NEW YORK CITY — The National September 11 Memorial & Museum commemoration ceremony will take place Sunday on the 9/11 Memorial plaza at the World Trade Center site in lower Manhattan.

The commemoration is for the family members of victims of the 2001 and 1993 attacks, and they have been invited to participate in this year’s reading of the names.

The 9/11 Memorial Museum will be open solely for family members, beginning at 8 a.m. The ceremony will pause at six moments – acknowledging when each of the World Trade Center towers was struck and fell, as well as the times corresponding to the attack on the Pentagon and the crash of Flight 93.

The first moment of silence will be at 8:46 a.m., and houses of worship have been asked to toll their bells at that time. The ceremony will conclude at about 12:30 p.m. 

Now, 21 years after the Sept. 11 terror attacks, these six moments of silence are part of the memorial ceremony. The public is invited to observe any or all of them.

Here is the list:

  • 8:46 a.m.: Hijackers crash Flight 11 into the north tower.
  • 9:03 a.m.: Hijackers crash United Airlines Flight 175 into the south tower.
  • 9:37 a.m.: Hijackers crash American Airlines Flight 77 into the Pentagon.
  • 9:59 a.m.: The south tower collapses.
  • 10:03 a.m.: Passengers launch a counterattack on hijackers aboard United Airlines Flight 93. The hijackers crash the plane into an empty field near Shanksville, PA.
  • 10:28 a.m.: The north tower collapses.
  • New York Harbor pre 9/11/2001 .Scanned from original 35mm negative showing statue of liberty in foreground and twin towers and lower Manhattan in background
  • The twin towers of the World Trade Center in lower Manhattan are shown in Feb. 1976. Atop the South Tower, right, is an observation deck. The Empire State Building can be seen in the background, center. (AP Photo)
  • A man fixes an American flag that was fallen from the position during a ceremony marking the 11th anniversary of the Sept. 11 terrorist attacks at the National September 11 Memorial at the World Trade Center site in New York, Tuesday, Sept. 11, 2012. (AP Photo/The New York Times, Chang W. Lee)
  • An undated photo of lower Manhattan Island, with the World Trade Center and World Financial center prominent in center. (AP Photo/Ed Bailey)