A New Jersey police officer holds an American Flag before the start of the ceremony at the 9/11 Memorial on the 23rd anniversary of the Sept. 11, 2001 terror attacks in New York. Photo: Pamela Smith / AP

Nearly 3,000 people were killed when al Qaida hijackers crashed four jetliners into the twin towers, the Pentagon and a field in southwest Pennsylvania.

On this day every morning for the past 23 years, families who lost loved ones in the worst terror attack on American soil make the solemn trek to observe the six moments of silence, hear the reading of the names, and fulfill a sacred promise to never forget.

As years pass, more and more names are being read by children and young adults born after the attacks - as an older generation passes on the grave responsibility of remembering this day to a new generation.

Wednesday's ceremony honors the 2,983 victims killed in the 2001 attacks on the World Trade Center, the Pentagon, aboard Flight 93 and in the 1993 WTC bombing.

The 9/11 Memorial & Museum opened to family members at 8:00 a.m. before the commemoration began at 8:46 a.m.

A citywide moment of silence was held at 8:46 a.m. to mark the moment hijacked Flight 11 struck the North Tower. A second moment of silence was held at 9:03 a.m. to mark when hijacked Flight 175 struck the South Tower.

Another moment of silence follows at 9:37 a.m., marking when hijacked Flight 77 struck the Pentagon.

A moment of silence will be held at 9:59 a.m. to mark when the South Tower fell, then at 10:03 a.m. to mark when hijacked Flight 93 crashed in Shanksville, Pennsylvania, and then at 10:28 a.m. to mark when the North Tower fell.

The ceremony typically concludes around 12:30 p.m.