NEW YORK, NEW YORK - SEPTEMBER 11: (L-R) 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 at the National 9/11 Memorial and Museum on September 11, 2021 in New York City. During the ceremony six moments of silence were held, marking when each of the World Trade Center towers was struck and fell and the times corresponding to the attack on the Pentagon and the crash of Flight 93. The nation is marking the 20th anniversary of the terror attacks of September 11, 2001, when the terrorist group al-Qaeda flew hijacked airplanes into the World Trade Center, Shanksville, PA and the Pentagon, killing nearly 3,000 people. (Photo by Chip Somodevilla/Getty Images)