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A meme posted on Facebook questions if planes could have taken down the twin towers during the 9/11 attacks on New York’s World Trade Center on 11 September 2001. Its evidence? The 1945 crash of a B-25 bomber – a type of military aircraft – into the city’s Empire State Building that left the building standing. The meme been shared over 100,000 times and was flagged as possibly false by Facebook’s fact-checking system , sending an alert for Africa Check to investigate . It shows a photo of a massive hole in the side of a skyscraper, with the caption : The 79th floor of the Empire State Building after a B-25 bomber crashed into it on July 28, 1945. Still believe planes took down the twin towers on 9/11? Can the first crash tell us anything useful about the second crash? And is this proof that something else caused the collapse of the World Trade Center towers? Twin towers secretly demolished? The 104-floor Empire State Building and 110-floor twin towers – One World Trade Center and Two World Trade Center – both held, at different times, the record as the tallest building in the world. The meme supports one argument of the 9/11 Truth Movement , or truthers, conspiracy theorists who believe that the US government is either withholding some vital information about the attacks or was somehow directly involved in them. One truther conspiracy theory is that a plane crash couldn’t have brought down a skyscraper, so the buildings must have been secretly demolished . We checked the available information. The crashes On 28 July 1945 , with heavy fog over New York, a US B-25 Mitchell military bomber lost its way and crashed into three storeys (floors 78 to 80) of the Empire State Building. A fire erupted and the crash left a 5.5- by 6-metre hole in the north side of the building. Fourteen people died. On 11 September 2001 , at 8:46 am, a hijacked plane crashed into seven storeys (floors 93 to 99) of One World Trade Center – the north tower – killing everyone on board and hundreds inside the building. A quarter of an hour later a second plane crashed into 11 storeys (floors 75 to 85) of the south tower , again killing all on board and hundreds more inside the building. Within an hour the south tower collapsed to the ground. Half an hour later, the first-struck north tower collapsed . It’s estimated that 2,753 people died as a result of the two crashes. The aircraft The photo in the meme is real and it is of the aftermath of the 1945 crash. But according to the aircraft website Aerospaceweb, there are multiple reasons why the crash caused relatively minor damage compared to the attacks on the twin towers . First, the B-25 bomber was not carrying a bomb load and was about to land so it had less fuel than usual and probably weighed close to its minimum weight of 9,579 kilograms . It was travelling at around 320 kilometres an hour at the time of impact. In comparison, the Boeing 767-200ER that hit One World Trade Center had an empty weight of 83,234 kilograms. According to the final report on 9/11 by the US National Institute of Standards and Technology (NIST), the plane was carrying half its maximum fuel load , five tonnes of luggage, mail, electronic equipment and food. The plane that hit Two World Trade Center, also a Boeing 767-200ER, was estimated to have been carrying 28,122 kilograms of jet fuel and 9 tonnes of luggage, mail, electronic equipment and food. Both Boeings would have been travelling 708 to 852 kilometres an hour at the times of impact . According to Aerospaceweb , before even accounting for the exploding energy from the jet fuel, the Boeings probably hit the twin towers with up to 100 times more impact than the lighter and slower B-25 bomber , allowing them to penetrate much further into the buildings. The type and quantity of jet fuel are another reason why the 9/11 attacks caused so much more destruction. The B-25 was running on avgas , a high-octane version of gasoline. But the Boeings were running on jet A , a derivative of kerosene that if atomised tends to burn more intensely than gasoline. The buildings The architecture of the buildings also played a role. According to Aerospaceweb, the Empire State Building’s structural steel beams are covered in limestone and concrete . The heavy mass of the stone insulates the structural steel beams from excessive heat. The major structural material used in the World Trade Centre towers was steel. Science and technology magazine Popular Mechanics has published a special report on 9/11 myths that put to rest the question of whether jet fuel can melt steel beams . It quotes senior engineer Farid Alfawakhiri of the American Institute of Steel Construction as saying: Steel loses about 50 per cent of its strength at 1100° Fahrenheit (593° Celsius). This is far below its melting temperature of 1,370°C. Steel does not have to melt for it to be compromised. What brought down the twin towers? According to a paper on materials and structures by civil engineering professors from the Massachusetts Institute of Technology , the impact of the aircraft is not what brought the buildings down. This is because the buildings were 2,500 times heavier than the aircraft. In fact, the B-25 crash prompted engineers to design the towers to withstand the impact of a large commercial aeroplane. And both buildings remained standing for at least 56 minutes after the initial impacts. Instead, it was the heat of the fires of burning jet fuel that weakened the structural steel beams and led to the failure of the elevated floor system . The floors at the top fell onto the ones below causing a freefall that was too powerful to be absorbed by the weakened steel structures below. This is a conclusion that the US Federal Emergency Management Agency and NIST agree with. – Africa Check
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