Six moments of silence were held to commemorate the 17th anniversary of the Sept. 11 terror attacks.
The first came at 8:46 a.m. to mark the moment hijackers crashed Flight 11 into the north tower of the World Trade Center.
The next came shortly after at 9:03 a.m., when the second struck the south tower.
Another moment of silence was held at 9:37 a.m., when Flight 77 crashed into the Pentagon.
At 9:59 a.m., the south tower of the World Trade Center collapsed.
At 10:03 a.m., passengers on Flight 93 attempted to thwart hijackers, leading the plane to crash into a field in Shanksville, Pennsylvania.
And finally, at 10:28 a.m., the north tower of the World Trade Center fell.
Nearly 3,000 people were killed in the attacks.