SEPTEMBER 11 2001 saw four co-ordinated suicide attacks against targets in New York and Washington, DC.
On that morning, 19 al-Qaeda terrorists hijacked four passenger jets and crashed two planes into the Twin Towers of the World Trade Centre, both towers collapsed within two hours.
A third plane crashed into the Pentagon in Arlington, Virginia.
When passengers attempted to take control of the fourth plane from hijackers, United Airlines Flight 93, it crashed into a field near Shanksville, Pennsylvania, preventing it from reaching its intended target in Washington, DC.
All on board were killed.
In 2004, Al-Qaeda leader Osama bin Laden, who had initially denied involvement, claimed responsibility for the attacks.
Al-Qaeda and bin Laden cited US. support of Israel, the presence of US. troops in Saudi Arabia, and sanctions against Iraq as motives for the attacks.
The United States, backed by British Prime Minister Tony Blair, responded by launching the War on Terror, invading Afghanistan to depose the Taliban, who had harboured al-Qaeda members.
In May 2011 bin Laden was found and killed.