September 9, 2011
Three unidentified rescue workers walk away from the crash site at the Pentagon in Arlington, Va., in this Sept. 11, 2001, file photo. In the most devastating terrorist onslaught ever waged against the United States, hijackers crashed two airliners into the World Trade Center, toppling its twin 110-story towers. The deadly calamity was witnessed on televisions across the world as another plane slammed into the Pentagon, and a fourth crashed outside Pittsburgh. This year marks the tenth anniversary of the attacks.