Somber ceremonies mark 9/11 anniversary

Pentagon's September 11th memorial

WASHINGTON (CNN) -- The somber music and voices of the United States Air Force Band at the Pentagon signaled the beginning of solemn memorial services Thursday to honor the victims of the September 11, 2001, terrorist attacks.

Seven years ago, al Qaeda terrorists used hijacked airplanes to attack the World Trade Center and the Pentagon -- the twin symbols of America's financial and military might. Another hijacked plane crashed in Pennsylvania.

At the Pentagon, the ceremony dedicated a memorial to the 184 victims killed when American Airlines Flight 77 struck the Pentagon's west wall.

A bagpiper walked alone across the Pentagon memorial playing "Amazing Grace." the rest

In pictures: Remembering 9/11