It was on September 11, 2001.
19 militants associated with the Islamic extremist group al-Qaeda hijacked four airplanes and carried out suicide attacks against targets in the United States.
Two of the planes were flown into the twin towers of the World Trade Center in New York City, a third plane hit the Pentagon just outside Washington, D.C., and the fourth plane crashed in a field in Pennsylvania.
The structural steel of the skyscraper, built to withstand winds in excess of 200 miles per hour and a large conventional fire, could not withstand the tremendous heat generated by the burning jet fuel.
At 10:30 a.m., the north building of the twin towers collapsed. Only six people in the World Trade Center towers at the time of their collapse survived. Almost 10,000 others were treated for injuries, many severe.
The US is marking the 16th anniversary of the 9/11 attacks which killed 2,997 people and injured more than 6,000.
It was the worst domestic attack the US had ever experienced, it directly led to then-President George Bush launching the "War on Terror", which continues to have ramifications today. Here are some of the archive images showing the immediate aftermath of the attacks shared by Independent.co.uk.