Harrowing images show true horror of 9/11, 18 years after tragedy that changed the world

On this day 18 years ago, hijacked planes hit the Twin Towers, killing thousands. It was a horror that will never be forgotten. WARNING: Distressing content

WARNING: Distressing content

On this day 18 years ago, unimaginable horror struck America when four commercial flights were hijacked by terrorists and crashed into sites including New York City’s Twin Towers.

The morning of Tuesday, September 11 was fine and sunny, with New Yorkers navigating the manic rush-hour commute to work or school under a cloudless blue sky.

But at 8.46am the unthinkable happened: American Airlines Flight 11, bound for Los Angeles, was hijacked by members of Al-Qaeda at Boston airport and flown into the North Tower of the World Trade Centre.

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People stared up in confusion and disbelief at the smoking building, wondering if perhaps it was an accident, until 17 minutes later a second plane, United Airlines Flight 175, hit the South Tower at 9.03am.

By 10.30am the Twin Towers had collapsed, sending people running for their lives covered in dust and debris. Meanwhile, 370 kilometres away, American Airlines Flight 77 was flown into the Pentagon building in Virginia at 9.37am, and United Airlines Flight 93 was crashed into a field near Shanksville, Pennsylvania, at 10.03am.

In less than two hours, 2996 people had been killed and more than 6000 injured, including hundreds of firefighters and police officers who rushed to the scenes.

This file photo taken on September 11, 2001 shows a hijacked commercial plane approaching the World Trade Centre shortly before crashing into the landmark skyscraper in New York. Picture: Seth McAllister/AFP

Photographs captured the horrific tragedy as it unfolded across America’s northeast, including heartbreaking images of people plunging to their deaths from the Twin Towers. One of these is the infamous “Falling Man” taken by Richard Drew. To this day the man’s identity is still unknown, but his clothing indicates he was an employee at the Windows on the World restaurant on the top floors (106th and 107th) of the North Tower.

While difficult to look at, pictures of one of the darkest days in modern history ensure the innocent lives lost at the hands of terrorists will never be forgotten.

Hijacked United Airlines Flight 175 aircraft about to fly into the second tower of the World Trade Centre. Picture: AP

A jet airliner is lined up on one of the World Trade Centre towers. Picture: Carmen Taylor/AP

A fiery blast rocks the south tower of the World Trade Centre as the hijacked United Airlines Flight 175 from Boston crashes into the building. Picture: Spencer Platt/Getty Images

Smoke and debris erupt from the south tower of the World Trade Centre as it collapses following the terrorist attacks on the buildings on September 11, 2001. Picture: Jerry Torrens, File/AP

People below look up as the World Trade Centre goes up in flames on September 11, 2001 in New York City. Picture: Spencer Platt/Getty Images

People hang from the windows of the North Tower of the World Trade Centre after a hijacked airliner hit the building on September 11, 2001 in New York City. Picture: Jose Jimenez/Primera Hora/Getty Images

A person falls to his death from the World Trade Centre after two planes hit the Twin Towers on September 11, 2001 in New York City. Picture: Jose Jimenez/Primera Hora/Getty Images

People watch from Sixth Ave in Soho as the towers collapse. Picture: Alamy

A man covered with dust stands outside the World Trade Centre after one of its towers collapsed on September 11, 2001 in New York City. Picture: Spencer Platt/Getty Images

This photo became known as ‘The Falling Man’ — the unknown man falls from the North Tower of the World Trade Centre at 9.41:15am on the morning of the terrorist attacks. Picture: Richard Drew/AP

Onlookers cry in the street as they watch the terror attacks unfold. Picture: Ernesto Mora/AP

An image from AP photographer Richard Drew's sequence of ‘The Falling Man’ taken at the World Trade Centre on 9/11. Picture: Richard Drew/AP

The World Trade Centre collapses on September 11, 2001. Picture: Alamy

A firefighter covered with ash is helped by a civilian after the World Trade Centre collapses in a terrorist attack. Picture: Thomas Monaster/NY Daily News Archive via Getty Images

A man leaps to his death from a fire and smoke-filled Tower One of the World Trade Centre on September 11, 2001 in New York City. Picture: Jose Jimenez/Primera Hora/Getty Images

A young woman cries in lower Manhattan following the terrorist attack on September 11, 2001. Picture: Don Halasy/Alamy

Secret Service agent Thomas Armas carries an injured woman to an ambulance after Tower One of the World Trade Centre collapsed. Picture: Thomas Monaster/NY Daily News Archive via Getty Images

Former chief of staff Andy Card whispers into the ear of then president George W. Bush to give him word of the plane crashes into the World Trade Centre during a visit to the Emma E. Booker Elementary School in Sarasota, Florida. Picture: Doug Mills/AP

People run from the collapse of one of the World Trade Centre towers on Tuesday, September 11, 2001 in New York City. Picture: Suzanne Plunkett/AP

Marcy Borders is covered in dust as she takes refuge in an office building after one of the World Trade Centre towers collapsed in New York City. Ms Borders was caught outside on the street as the cloud of smoke and dust enveloped the area. Picture: Stan Honda/AFP

Pedestrians run from the scene as one of the World Trade Centre towers collapses in this September 11, 2001 file photo. Picture: Doug Kanter/AFP

An image from AP photographer Richard Drew. Picture: Richard Drew/AP

Police officer Michael Brennan helps a woman named Beverly to safety. She was covered in dust after the first tower went down. Picture: Joey Newfield/NY Post

This and other aerial photos from the 9/11 attacks were obtained by ABC News, which in 2009 filed a Freedom of Information Act request with the National Institute of Standards and Technology. Picture: ABC News/NYPD/Detective Greg Semendinger via AFP

Joseph Kelly, Srinath Jinadasa and George Sleigh covered in dust and debris as they walk away from the World Trade Centre. Picture: Splash News

FBI agents, firefighters, rescue workers and engineers work at the Pentagon crash site on September 14, 2001, where a hijacked American Airlines flight slammed into the building on September 11. The terrorist attack caused extensive damage to the west face of the building and followed similar attacks on the twin towers of the World Trade Centre in New York City. Picture: Department of Defence/ Tech Sgt Cedric H. Rudisill

Emergency vehicles at the devastated Pentagon on September 11, 2001 in Washington, DC, hours after a hijacked plane crashed into the facility, the centre of the US military, in a terrorist attack. Picture: Stephen Jaffe/AFP

East side of the World Financial Centre on the Hudson River on September 17, 2001. The glass roof of the Winter Garden, a public space with full-size palm trees, is damaged and covered with debris from the Twin Towers. In the upper left is the Yacht Basin on the Hudson River. Picture: Alamy

A health club in the World Financial Centre after the 9/11 attacks. Picture: Alamy

A New York firefighter is overcome with emotion following the 9/11 attacks. Picture: Universal History Archive/UIG via Getty Images

An aerial view of the destruction by terrorists of the World Trade Centre on September 15, 2001 in New York City. The view is to the west, with an American flag draped on one of the World Financial Centre towers. Picture: Alamy

Picture found in the dust at the World Trade Centre ground zero. Picture: Nathan Edwards/News Corp

An ash-covered man helps a woman following the terrorist attack on the World Trade Centre in New York City on September 11, 2001. Picture: Don Halasy/Alamy

The sequence shows the collapse of the World Trade Centre in New York City on September 11, 2001. Picture: AFP

A police officer reaches into a debris and ash-covered police car in lower Manhattan. Picture: Alamy

A rescuer on a break surrounded by the eerie reminder of what once was a bustling area of world commerce. Picture: Alamy

Personal effects were hastily abandoned when buildings were evacuated in the wake of the September 11, 2001 terrorist attack on the World Trade Centre. Picture: Alamy

What was once a glittering symbol of the financial centre of the world stood blanketed in ash and soot. Picture: Jim Watson/Alamy

NYC firemen check a car on Barclay St after the 9/11 terrorist attack on the World Trade Centre. Picture: Alamy

A New York City fireman calls for 10 more rescue workers to make their way into the rubble of the World Trade Centre. Picture: Alamy

Ground Zero. Picture: Nathan Edwards/News Corp

A dust covered ambulance in the remains of the World Trade Centre. Picture: Alamy

The rubble of the World Trade Centre. Picture: Alex Fuchs/AFP

Brooklyn firefighters George Johnson (left) of ladder 157, Dan McWilliams (centre) of ladder 157, and Billy Eisengrein (right) of Rescue 2, raise a flag at the World Trade Centre in New York. Picture: Thomas E. Franklin/AP