On September 11, 2001, a series of coordinated terrorist attacks against the United States by the extremist group al-Qaeda - the largest and most devastating attacks in American history - took place in New York City. Here's a look back at those tragic events, 22 years ago, which were felt around the world.
A look back at 9/11
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Firefighters head for the World Trade Center after two planes, American Airlines Flight 11 and United Airlines Flight 175, crashed into the North and South Towers of the World Trade Center in Lower Manhattan, New York.
A look back at 9/11
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People look at the burning World Trade Center as, at 8:46 a.m., Flight 11 became the first plane to reach its target when it deliberately crashed into the North Tower of the WTC.
A look back at 9/11
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At 9:03 a.m., Flight 175 strikes the South Tower of the World Trade Center.
A look back at 9/11
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Thousands of people are trapped in the burning skyscrapers, and the images travel around the world.
A look back at 9/11
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The South Tower collapsed at 9:58 a.m., followed by the North Tower 29 minutes later.
A look back at 9/11
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The attacks triggered a massive emergency response, with firefighters, police and first responders rushing to the scene in New York.
A look back at 9/11
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Their courage and heroism were on full display as they worked tirelessly to save lives and provide aid.
A look back at 9/11
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However, the scale of the attacks and the devastation seemed too powerful.
A look back at 9/11
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The 9/11 attacks had far-reaching consequences. The loss of life, physical destruction and economic and psychological impact were immense. The United States, under President George W. Bush, then launched the War on Terror, targeting Al Qaeda and its supporters in Afghanistan and later in Iraq.
A look back at 9/11
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The destruction of the Twin Towers was a catastrophic event that resulted in the loss of almost 3,000 lives, including employees, rescue workers and passengers on hijacked planes.
A look back at 9/11
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Rescuers scour the rubble of the World Trade Center, a few days after the terrorist attack.
A look back at 9/11
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New York firefighters worked around the clock at the World Trade Center in the days following the attacks, despite the death of several of their colleagues.
A look back at 9/11
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The official end of clean-up operations at Ground Zero was declared on May 30, 2002, when the last steel beam from the World Trade Center site was ceremoniously removed. The clean-up process was a massive and difficult undertaking, involving numerous agencies, construction workers, first responders and volunteers working tirelessly to clear the site and recover the remains of the victims. It was certainly an emotionally-charged operation.
A look back at 9/11
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In addition to the World Trade Center attacks, a third plane, American Airlines Flight 77, crashed into the Pentagon. A fourth hijacked plane, United Airlines Flight 93, was headed for a target in Washington D.C., but the passengers on board fought back against the terrorists. The plane eventually crashed in a Pennsylvania field.