A third plane hit the Pentagon, killing The fourth hijacked plane was crashed into a field in Shanksville, Pennsylvania that killed 40 more. A plane flying from Boston to Los Angeles with 92 people on board, including five hijackers, was crashed into the North Tower of the World Trade Center at am local time. An hour and 42 minutes after the impact, the North Tower collapsed, releasing a huge cloud of dust and smoke. At am local time , another plane with 65 people on board — including five hijackers — hit the South Tower, sparking a massive explosion and collapsed 56 minutes later.
Source: AFP. Besides the twin towers, a storey third tower, known as Tower Seven, was also collapsed after seven hours on the same day. Meanwhile, United Airlines Flight 93 crashed near Shanksville, Pennsylvania, after passengers tried to take control of the plane from the hijackers. Online theories claim it was shot down by a white business jet flying into a nearby airport.
But aviation officials had requested the jet inspect the area, which it did, reporting back evidence of a big hole in the ground with smoke coming out of it.
Vice-President Dick Cheney later revealed in his autobiography that following the attack on the Twin Towers, he had ordered the shooting down of any commercial airliner believed to have been hijacked. Another theory falsely claims no Jewish people were killed in the attacks because 4, Jewish employees at the World Trade Center had received advance notice not to turn up for work. Believers conclude the Israeli government mounted the attacks to goad the US into attacking its regional enemies or responsibility lies with powerful Jewish elites who control world events from the shadows.
That would constitute 9. And some estimate up to Jewish people might have died that day. Similar theories surround other states, including Iraq and Iran, but no evidence of their direct involvement has ever been found. Image source, Getty Images. Online conspiracy-theory platforms continue to push claims of US involvement in the attacks. Uncontrolled fires. It is understood the South Tower collapsed sooner because it suffered more damage from the initial aircraft impact, which also dislodged more fireproofing material.
While there are different theories regarding how the progressive collapse of Building 7 was initiated, there is consensus among investigators fire was the primary cause of failure.
Both official reports made a range of fire safety recommendations for other high-rise buildings, including to improve evacuation and emergency response. In , the National Institute of Standards and Technology also published a best practice guide recommending solutions to reduce risk of progressive collapse.
There have since been changes to building codes and standards on improving the structural performance of buildings on fire, as well as opportunities to escape such as added stairwell requirements. At the same time, the collapse of the twin towers demonstrated the very real dangers of fire in high-rise buildings. In the decades since the World Trade Center was designed, buildings have become taller and more complex, as societies demand sustainable and cost-effective housing in large cities. This can be partly attributed to the wide use of flammable cladding.
It is marketed as an innovative, cost-effective and sustainable material, yet it has shown significant shortcomings in terms of fire safety — as witnessed in the Grenfell Disaster. The Grenfell fire and similar cladding fires are proof that fire safety in tall buildings is still a problem.
And as structures get taller and more complex, with new and innovative designs and materials, questions around fire safety will only become more difficult to answer. Read more: Cladding fire risks have been known for years.
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