At 8:46am (New York time), American Airlines Flight 11 (travelling from Boston to Los Angeles) strikes the north tower of the World Trade Center in New York City.
Seventeen minutes later, at 9:03am, United Airlines Flight 175 (travelling from Boston to Los Angeles) slams into the south tower of the World Trade Center.
At the World Trade Center, 2,753 people were killed when Flight 11 and Flight 175 crashed into the north and south towers, or as a result of the crashes.
Of those who perished during the initial attacks and the subsequent collapses of the towers, 343 were New York City firefighters, 23 were New York City police officers and 37 were officers at the Port Authority.
The South Tower spectacularly almost bends in half and comes crashing to the ground. Victims who died in the attack ranged in age from two to 85 years. Approximately 75-80% of the victims were men.
The attack on the WTC was orchestrated by al Qaeda leader Osama bin Laden, who was finally caught and shot dead almost ten years later.
The World Trade Center burns after two planes strike one of the most recognisable structures in Manhattan. At the Pentagon in Washington, 184 people are killed when hijacked American Airlines Flight 77 crashed into the building.
US President George W. Bush speaks to Vice President Dick Cheney by phone aboard Air Force One September 11, 2001 after departing Offutt Air Force Base in Nebraska.
In surreal scenes, less than an hour after Flight 175 hit, the south tower of WTC collapses at 9:59am in approximately 10 seconds. Four days later (pictured) clouds of smoke continue to rise from the rubble and into the New York sky.
People run from the collapse of World Trade Center Tower. A man named Charlie Ross is seen fourth from the left.