As America remembers September 11, 2001, we look back at how the tragedy unfolded.
It was a clear, sunny day when Al-Qaeda terrorists hijacked four passenger planes and crashed two into the World Trade Centre and one into the Pentagon.
Passengers on the fourth plane fought back and the aircraft crashed into a field in Pennsylvania, killing everyone on board. A total of nearly 3,000 people lost their lives in the tragedy.
The airplanes hijacked on 9/11 begin taking off at 7:59 am, two from Boston, one from Washington and one from Newark, carrying a total of 265 people.
The first crash occurs at 8:46 am, when Flight 11 slams into the north tower of New York's World Trade Centre.
The second crash comes at 9:03am, when Flight 175 flies into the south tower of the World Trade Centre.
President George W. Bush learns of the attacks while sitting in a second grade classroom at Emma Booker Elementary School in Sarasota, Florida.
In an address from the school, Bush calls the attacks "a national tragedy" and "an apparent terrorist attack on our country."
Flight 77 crashes into the Pentagon.
After burning for 56 minutes, the south tower of the World Trade Centre collapses.
The fourth hijacked plane crashes in a field in Shanksville, Pennsylvania.
After burning for 102 minutes, the north tower of New York's World Trade Centre collapses.
New York City Mayor Rudy Giuliani orders an evacuation of lower Manhattan, alerting everyone south of Canal Street to leave.
After all American air space has been cleared, Bush addresses the nation from Barksdale Air Force Base in Louisiana, informing citizens that the US military "at home and around the world is on high alert status."