Secretary of Defense Mark Esper takes part in a wreath ceremony at the entrance to the Department of Defense headquarters Friday morning, alongside Chairman of the Joint Chiefs of Staff Mark Milley. 

That was followed by a moment of silence at 9:37, marking the moment American Airlines flight 77 crashed into the Pentagon, killing all 64 people on the plane and 125 people in the building. 

Relatives of those killed did not attend the ceremony on the 19th anniversary of 9/11 due to the COVID-19 pandemic. However, they are being allowed to visit the site later in the day.