In September 2001, al-Qaeda terrorists violently commandeered four passenger planes, crashing two of them into the twin towers of the World Trade Center in New York and another into the Pentagon.
The fourth jet came down in a field in Pennsylvania after being initially directed toward Washington.
Some 3,000 people from 90 countries lost their lives in the terrorist attacks, while another estimated 3,000 have succumbed since that time to diseases caused by working around 'Ground Zero', the site of the collapsed towers.
WARNING: Some of the following photos may offend sensibilities
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© AP Photo / Will Morris
In this 11 September 2001 file photo, damage to the outer ring of the Pentagon is shown after a hijacked airliner crashed into the building.
A police officer helps a woman to a bus after she fled the area near the World Trade Center towers on 11 September 2001, in New York.
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© AP Photo / Mike Derer
The World Trade Center is seen burning in New York City in this view from Liberty State Park in Jersey City, N.J., after the attacks on the towers and at the Pentagon in Washington.
New York City firemen walk past the American flag as they work their way toward the heart of the devastation that was once the World Trade Center.
A Pentagon official outside the Pentagon, from which smoke is billowing following the 11 September 2001 attack.
An aerial view shows a small portion of the scene where the World Trade Center collapsed following the 11 September terrorist attack
New York City firefighters take a much-needed break during emergency response efforts following the 9/11 attacks.
WARNING: The photo above may be unsuitable for some viewers.
A person falls to his death from the World Trade Center after two planes hit the Twin Towers on 11 September 2001, in New York City.
A person falls to his death from the World Trade Center after two planes hit the Twin Towers on 11 September 2001, in New York City.
Rescue workers work late on 18 September 2001 in Washington, DC, sifting through piles of debris from the section of the Pentagon hit by the terrorist attack 11 September
Then-US President George W. Bush (C) and then-US Secretary of Defence Donald Rumsfeld (L) tour the impact area (rear) at the Pentagon on 12 September 2001, where a hijacked airline was crashed into the building as part of a coordinated terrorist attack on the US.
A US Navy videographer documents the crime scene where the World Trade Center collapsed following the 11 September terrorist attack.
Personal belongings were hastily abandoned when buildings were evacuated in the wake of the 11 September, terrorist attack on the World Trade Center.
Fires still burn amidst the rubble of the World Trade Center, days after the 11 September terrorist attack.
A firefighter emerges from the smoke and debris of the World Trade Center.
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© AP Photo / Ernesto Mora
The south tower of the World Trade Center erupts in flames as it is struck by a second plane in a terrorist attack on the landmark complex.
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© AP Photo / Gulnara Samoilova
Survivors of the terrorist attacks on the World Trade Center in New York make their way through smoke, dust and debris on Fulton St., about a block from the collapsed towers in this Tuesday, September 11, 2001 file photo.
An aerial view shows a small portion of the crime scene where the World Trade Center collapsed following the 11 September terrorist attack.
A man with a fire extinguisher walks through rubble after the collapse of the first World Trade Center Tower on 11 September 2001, in New York. The man was shouting as he walked looking for victims who needed assistance.
