Photos: A recap of events marking the 20th anniversary of 9/11

Television crews prepare for coverage of the 20th anniversary of Sept. 11, 2001, terrorist attacks on Friday, Sept. 10, 2021, at the Pentagon in Washington. (AP Photo/Jacquelyn Martin)

A person touches an inscribed name at the National September 11 Memorial and Museum ahead of the 20th anniversary of the 9/11 terrorist attacks, Friday, Sept. 10, 2021, in New York. (AP Photo/Matt Rourke)

People visit the National September 11 Memorial and Museum ahead of the 20th anniversary of the 9/11 terrorist attacks, Friday, Sept. 10, 2021, in New York. (AP Photo/Matt Rourke)

Visitors to the Flight 93 National Memorial in Shanksville, Pa., participate in a sunset memorial service, Friday, Sept. 10, 2021, as the nation prepares to mark the 20th anniversary of the Sept. 11, 2001, attacks. (AP Photo/Gene J. Puskar)

The World Trade Center is shown on the evening of Friday, Sept. 10, 2021, in New York. Saturday marks the 20th anniversary of the attacks of Sept. 11, 2001. (AP Photo/Mark Lennihan)

A beam of light is visible over the Lincoln Memorial, the day before the 20th anniversary of the Sept. 11 terrorist attacks, as part of the Towers of Light Tribute near the Pentagon, Friday Sept. 10, 2021, in Washington. (AP Photo/Jose Luis Magana)

President Barack Obama stands with others before ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

A couple embraces near the end of an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. (AP Photo/Alex Brandon)

President Joe Biden waves as he and first lady Jill Biden board Air Force One at John F. Kennedy International Airport in the Queens borough of New York, Saturday, Sept. 11, 2021. The Bidens are en route to the Flight 93 National Memorial in Shanksville, Pa., for an event marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks. (AP Photo/Evan Vucci)

A ceremonial bell rests on a stage podium at the start of ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

A person places flowers and a U.S. flag on a name inscribed on the National September 11 Memorial on the 20th anniversary of the terrorist attacks in New York, Saturday, Sept. 11, 2021. (Mike Segar/Pool Photo via AP)

Vice President Kamala Harris and her husband Douglas Emhoff attend a memorial for the passengers and crew of United Flight 93, Saturday Sept. 11, 2021, in Shanksville, Pa., on the 20th anniversary of the Sept. 11, 2001, attacks. Secretary of Interior Deb Haaland and Gordon Felt, brother of Edward Porter Felt and President of Familes for Flight 93, are right. (AP Photo/Jacquelyn Martin)

A person holds an image of a victim during ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (Mike Segar /Pool Photo via AP)

An attendee salutes as taps are played during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. (AP Photo/Alex Brandon)

Former Secretary of State Hillary Clinton, 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 a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Joint Chiefs Chairman Gen. Mark Milley, speaks during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks.(AP Photo/Alex Brandon)

People react as they attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

People react as they attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

A person carries a depiction of an American flag near one of the reflecting pools at the National September 11 Memorial and Museum as people attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Firefighters from Massachusetts gather with others outside the National September 11 Memorial and Museum during a ceremony marking the 20th anniversary of the 9/11 terrorist attacks, Saturday, Sept. 11, 2021, in New York. (AP Photo/Matt Rourke)

A person is detained near the National September 11 Memorial & Museum during a ceremony marking the 20th anniversary of the 9/11 terrorist attacks, Saturday, Sept. 11, 2021, in New York. (AP Photo/Matt Rourke)

A mourner stands at the south pool before ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

Former President Barack Obama, former first lady Michelle Obama, President Joe Biden and first lady Jill Biden attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Vice President Kamala Harris and her husband Douglas Emhoff, attend a memorial for the passengers and crew of United Flight 93, Saturday Sept. 11, 2021, in Shanksville, Pa., on the 20th anniversary of the Sept. 11, 2001, attacks. (AP Photo/Jacquelyn Martin)

Secretary of Defense Lloyd Austin speaks during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. An American flag is draped over the site of impact at the Pentagon. (AP Photo/Alex Brandon)

Secretary of Defense Lloyd Austin, accompanied by Joint Chiefs Chairman Gen. Mark Milley, seated left, speaks during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. (AP Photo/Alex Brandon)

Former New York City mayor Rudy Giuliani attends ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

Former President Barack Obama, former first lady Michelle Obama and President Joe Biden attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Vice President Kamala Harris and her husband Douglas Emhoff arrive to board Air Force Two at Andrews Air Force Base, Md., on Saturday, Sept. 11, 2021, en route to Shanksville, Pa., to attend a memorial for the passengers and crew of United Flight 93, on the 20th anniversary of the Sept. 11, 2001, attacks. They are escorted by Lt. Col Timothy Fritz, right. (AP Photo/Jacquelyn Martin)

Flag bearers rehearse before ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

Flowers placed at the name of Frank Spinelli before ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (Anthony Behar, Pool Photo via AP)

Arlington, Va Fire Department ladder trucks fly an American flag prior to an observance ceremony on the morning of the 20th anniversary of the terrorist attacks, Saturday, Sept. 11, 2021, at the Pentagon in Washington. (AP Photo/Alex Brandon)

Katie Mascali is comforted by her fiancee Andre Jabban as they stand near the name of her father Joseph Mascali, with FDNY Rescue 5, as they attend ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021 in New York. (Craig Ruttle/Newsday via AP, Pool)

Former President Barack Obama, former first lady Michelle Obama, President Joe Biden, and first lady Jill Biden attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Former President Barack Obama, former first lady Michelle Obama, President Joe Biden and first lady Jill Biden attend a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Former President Barack Obama, former First Lady Michelle Obama, President Joe Biden, and First Lady Dr. Jill Biden, attend ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

Secretary of Defense Lloyd Austin, front left, accompanied by Joint Chiefs Chairman Gen. Mark Milley, right, participates in an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. (AP Photo/Alex Brandon)

Former President Bill Clinton, left, and former Secretary of State Hillary Clinton attend ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

Bruce Springsteen performs during a ceremony marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks at the National September 11 Memorial and Museum in New York, Saturday, Sept. 11, 2021. (AP Photo/Evan Vucci)

Attendees listen during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. An American flag is draped over the site of impact at the Pentagon. (AP Photo/Alex Brandon)

An attendee prays during an observance ceremony at the Pentagon in Washington, Saturday, Sept. 11, 2021, on the morning of the 20th anniversary of the terrorist attacks. (AP Photo/Alex Brandon)

A beam of light is visible over the World War II Memorial, the day before the 20th anniversary of the Sept. 11 terrorist attacks, as part of the Towers of Light Tribute near the Pentagon, Friday Sept. 10, 2021, in Washington. (AP Photo/Jose Luis Magana)

An American flag is unfurled at the Pentagon in Washington, Saturday, Sept. 11, 2021, at sunrise on the morning of the 20th anniversary of the terrorist attacks. The American flag is draped over the site of impact at the Pentagon. In the foreground, the National 9/11 Pentagon Memorial, opened in 2008 adjacent to the site, commemorates the lives lost at the Pentagon and onboard American Airlines Flight 77. (AP Photo/Alex Brandon)

An American flag is unfurled at the Pentagon in Washington, Saturday, Sept. 11, 2021, at sunrise on the morning of the 20th anniversary of the terrorist attacks. The American flag is draped over the site of impact at the Pentagon. In the foreground, the National 9/11 Pentagon Memorial, opened in 2008 adjacent to the site, commemorates the lives lost at the Pentagon and onboard American Airlines Flight 77. (AP Photo/Alex Brandon)

An American flag is unfurled at the Pentagon in Washington, Saturday, Sept. 11, 2021, at sunrise on the morning of the 20th anniversary of the terrorist attacks. The American flag is draped over the site of impact at the Pentagon. (AP Photo/J. Scott Applewhite)

The Pentagon is illuminated at dawn before ceremonies marking the 20th anniversary of the Sept. 11, 2001, terrorist attacks in Washington, Saturday, Sept. 11, 2021. (AP Photo/J. Scott Applewhite)

Vice President Kamala Harris and her husband Douglas Emhoff arrive to board Air Force Two at Andrews Air Force Base, Md., on Saturday, Sept. 11, 2021, en route to Shanksville, Pa., to attend a memorial for the passengers and crew of United Flight 93, on the 20th anniversary of the Sept. 11, 2001, attacks. They are escorted by Lt. Col Timothy Fritz, right, and SSgt Aleasha Duggins, left. (AP Photo/Jacquelyn Martin)

The casket of Sgt. Johanny Rosario Pichardo, a U.S. Marine who was among 13 service members killed in a suicide bombing in Afghanistan, is carried into the Farrah Funeral Home in her hometown of Lawrence, Mass, Saturday, Sept. 11, 2021. (AP Photo/Robert F. Bukaty)

Members of the public arrive to the south pool after the conclusion of ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/John Minchillo)

President Joe Biden, first lady Jill Biden, Vice President Kamala Harris and her husband Douglas Emhoff, participate in a wreath ceremony on the 20th anniversary of the terrorist attacks at the Pentagon in Washington, Saturday, Sept. 11, 2021, standing at the National 9/11 Pentagon Memorial site, which commemorates the lives lost at the Pentagon and onboard American Airlines Flight 77. With the President, not shown, are Secretary of Defense Lloyd Austin and Joint Chiefs Chairman Gen. Mark Milley and his wife Hollyanne Milley. (AP Photo/Alex Brandon)

President Joe Biden walks at the National 9/11 Pentagon Memorial site, which commemorates the lives lost at the Pentagon and onboard American Airlines Flight 77, after participating in a wreath ceremony on the 20th anniversary of the terrorist attacks at the Pentagon in Washington, Saturday, Sept. 11, 2021. Shown with the President are Vice President Kamala Harris and her husband Douglas Emhoff, first lady Jill Biden, Joint Chiefs Chairman Gen. Mark Milley and his wife Hollyanne Milley,. (AP Photo/Alex Brandon)

Richard Sidell pays his respect to the friends who were killed, at the south pool after the conclusion of ceremonies to commemorate the 20th anniversary of the Sept. 11 terrorist attacks, Saturday, Sept. 11, 2021, at the National September 11 Memorial & Museum in New York. (AP Photo/Matt Rourke)

Navy's marching band performs at halftime during an NCAA college football game between Navy and Air Force, Saturday, Sept. 11, 2021, in Annapolis, Md. (AP Photo/Terrance Williams)

Navy's marching band performs at halftime during an NCAA college football game between Navy and Air Force, Saturday, Sept. 11, 2021, in Annapolis, Md. (AP Photo/Terrance Williams)

The Brigade of Midshipmen stand at attention during the National Anthem before an NCAA college football game between Navy and Air Force, Saturday, Sept. 11, 2021, in Annapolis, Md. (AP Photo/Terrance Williams)

The pit crew of Noah Gragson (9) displays the U.S. flag during laps nine, ten and eleven during the NASCAR Xfinity auto race in Richmond, Va., Saturday, Sept. 11, 2021. (AP Photo/Steve Helber)

To commemorate the 20th anniversary of 9/11, the 155th Air Refueling Wing of Lincoln, Neb., flies a KC-135 Stratotanker, center, alongside three F-16 Fighting Falcons flown by the 114th Fighter Wing of Sioux Falls, South Dakota, over Memorial Stadium during the playing of the national anthem before Buffalo plays against Nebraska in an NCAA college football game, Saturday, Sept. 11, 2021, in Lincoln, Neb. (AP Photo/Rebecca S. Gratz)

The Brigade of Midshipmen stand at attention during the National Anthem before an NCAA college football game between Navy and Air Force, Saturday, Sept. 11, 2021, in Annapolis, Md. (AP Photo/Terrance Williams)

The Brigade of Midshipmen stand at attention during pre-game ceremonies before an NCAA college football game between Navy and Air Force, Saturday, Sept. 11, 2021, in Annapolis, Md. (AP Photo/Terrance Williams)

The New York Yankees and the New York Mets line up together along the baselines for the 20th anniversary of the 9/11 terrorist attacks before a baseball game on Saturday, Sept. 11, 2021, in New York. (AP Photo/Adam Hunger)

The New York Yankees and the New York Mets line up together along the baselines for the 20th anniversary of the 9/11 terrorist attacks before a baseball game on Saturday, Sept. 11, 2021, in New York. (AP Photo/Adam Hunger)

New York Mets fans wear jerseys to remember the 20th anniversary of the 9/11 terrorist attacks before a baseball game against the New York Yankees on Saturday, Sept. 11, 2021, in New York. (AP Photo/Adam Hunger)

Former New York Yankees manager Joe Torre, left, and former New York Mets manager Bobby Valentine react after they threw out ceremonial first pitches before a baseball game Saturday, Sept. 11, 2021, in New York. (Andrew Mills/NJ Advance Media via AP)

Former President George W. Bush speaks during a memorial for the passengers and crew of United Flight 93, Saturday Sept. 11, 2021, in Shanksville, Pa., on the 20th anniversary of the Sept. 11, 2001 attacks. (AP Photo/Jacquelyn Martin)

Former President George W. Bush speaks at the Flight 93 National Memorial in Shanksville, Pa., Saturday, Sept. 11, 2021, on the 20th anniversary of the Sept. 11, 2001 attacks. (AP Photo/Gene J. Puskar)

Former President George W. Bush, right, wipes his eyes next to former first lady Laura Bush, after he spoke at a memorial for the passengers and crew of United Flight 93, Saturday, Sept. 11, 2021, in Shanksville, Pa., on the 20th anniversary of the Sept. 11, 2001, attacks. (AP Photo/Jacquelyn Martin)

Former President George W. Bush, right center, bumps fists with Flight 93 National Memorial superintendent Stephen M. Clark, left, after participating in a Service of Remembrance at the Flight 93 National Memorial in Shanksville, Pa., Saturday, Sept. 11, 2021, as the nation marks the 20th anniversary of the Sept. 11, 2001 attacks. (AP Photo/Gene J. Puskar)