Photos: Remembering those lost 20 years ago on 9/11

From left: Former President Barack Obama, former First Lady Michelle Obama, President Joe Biden, First Lady Jill Biden and former New York City Mayor Michael Bloomberg attend the annual 9/11 Commemoration Ceremony on Sept. 11, 2021 in New York.

A man cries at a ceremony at Ground Zero held in commemoration of the 20th anniversary of the terrorist attacks.

Members of the New York Police and Fire Department hold a flag for the national anthem during the commemoration ceremony.

American flags adorn the South Tower reflecting pool in lower Manhattan.

Firefighters and others take part in a moment of silence in New York.

A man weeps as he remembers the fallen during a ceremony in lower Manhattan.

Former President George W. Bush reflects during a ceremony at the Flight 93 National Memorial in Shanksville, Pa.

Vice President Harris speaks in Shanksville, Pa.

A National Park Service ranger stands in front of the Wall of Names at the Flight 93 National Memorial in Shanksville, Pa.

President Biden and First Lady Jill Biden lay a wreath at the Flight 93 National Memorial in Shanksville, Pa.

Port Authority Police officers pause during the annual commemoration ceremony at the National 9/11 Memorial in New York City.

Former New York City Mayor Rudy Giuliani attends the memorial in lower Manhattan.

An American flag is unfurled at dawn over the Pentagon in Arlington, Va.

A family member grieves at the World Trade Center site.

A man plays a trumpet during a ceremony in Weehawken, N.J.

People gather beneath the Freedom Tower as the city of New York commemorates the 20th anniversary of the September 11th terrorist attacks.