Remembering 9/11
MLADEN ANTONOV/AFP/Getty Images
US pop singer and song writer Paul Simon performs during the ceremony marking the 10th anniversary of the 9/11 terrorist attacks on the World Trade Center in New York on September 11, 2011. Al-Qaeda hijackers crashed passenger planes into the World Trade Center in New York and the Pentagon in Washington, while a fourth jet crashed in Shanksville, Pennsylvania.