On Tuesday morning, September 11, 2001, the U.S. came under...

09/11/2014 10:57 AM EDT

On Tuesday morning, September 11, 2001, the U.S. came under attack when four commercial airliners were hijacked and used to strike targets on the ground. Nearly 3,000 people tragically lost their lives. Because of the actions of the 40 passengers and crew aboard one of the planes, Flight 93, the attack on the U.S. Capitol was thwarted. 

Today the National Park Service, its volunteers, and its partners work to honor their sacrifice and to try to understand more fully the legacy of Flight 93 and the other events of 9/11.

Photo from the Flight 93 National Memorial: Tami A. Heilemann