Nearly 3,000 people were killed when the hijacked planes were flown into the World Trade Center in New York City, the Pentagon near Washington, DC, and when United Airlines Flight 93 crashed in the Pennsylvania countryside outside of Shanksville, PA.

On the morning of September 11, 2001, the third hijacked aircraft, American Airlines Flight 77, did not "land" in the traditional sense; rather, it was crashed into the western facade of The Pentagon in Arlington, Virginia, just outside Washington, D.C. The Boeing 757 had departed from Washington Dulles International Airport bound for Los Angeles before it was overtaken by five hijackers. At 9:37 AM EDT, the plane struck the first floor of the Pentagon's western wedge, penetrating three of the building's five concentric rings. The impact and subsequent fire caused the deaths of all 64 people on board (including the hijackers) and 125 personnel inside the building. This third strike followed the two impacts at the Twin Towers in New York City and preceded the crash of the fourth plane, United Flight 93, in a field near Shanksville, Pennsylvania. The site at the Pentagon now features a permanent outdoor memorial consisting of 184 illuminated benches, each dedicated to a victim of the attack on that specific location.