On the 11th of September of 2001, 4 where hijacked and used to crash into buildings in the US. 2 of the planes which got hijacked, crashed into the north and south tower of the world trade center complex. 3000 people died from the crash and the rubble that came flying afterwards.
Within 1 hour and 42 minutes both towers had collapsed and 15 nearby buildings had been severely damaged.
Today the 2 towers that had collapsed and the buildings that also were damaged have been completely restored. Although the damage done to the USA may never heal, this incident was caused by al-Qaeda and had struck a mighty blow to the citizens of USA.