These are the most common conspiracy theories about the September 11 attacks:
Conspiracy theories about the September 11 attacks basically state that:
1) The World Trade Center towers were demolished with silent controlled explosions.
2) The United States Air Force allowed these attacks to happen by staying passive on the ground.
3) There was unusual behavior on the stock market during the days leading up to September 11 with the sale of shares of companies affected by the attacks, suggesting that a group of people in the United States knew in advance that these events were on the way to happen.
4) Foreign governments such as Israel or Saudi Arabia were involved in the attacks.
These are the refutations to these theories:
• No remains of termite compounds or other materials that could have caused an intentional silent collapse of the buildings were found in the rubble. The publications that support this theory have not been able to present yet any scientific evidence for this and several editors of the journals that published these articles were removed due to the lack of scientific standards on the part of the authors.
The strongest explanation for how the three World Trade Center Towers (Twin Towers and Building #7) collapsed is that the heat generated by the explosions of the aircrafts, and the fire that followed it, weakened the steel structures on all floors where there was a fire. Out of the steel that composed the columns, the buildings were made of very soft materials in the walls and floors of the offices, and not like as a stone building. Engineering models show that it was sufficient that more than four floors of the World Trade Center towers had caught fire for the weight of these floors make the rest of the building's structure to collapse. In 2017 and 2018, for example, two buildings in Tehran and Sao Paulo respectively, went down completely in a similar way to the World Trade Center after experiencing also fires on the upper floors.
• The terrorists turned off the gps and thus prevented to locate the exact position of the hijacked planes. Incredibly, until that date, the United States Military Air Command had no direct communication with controllers in civilian airport towers. The last incident that involved hijacked plane in the United States prior to the September 11 attacks had been in 1979 and the response time for the military planes to approach that plane was 79 min. In the case of the Twin Towers, the military was notified less than ten minutes before the impact, which made any prompt response impossible to achieve.
• It is true that there was a massive sale of shares of American Airlines, United Airlines, Citigroup and insurers that had offices in the Twin Towers, but no suspicious relationship has been found between these stock market events and the September 11 attacks. In the case of United Airlines shares, the majority of the money obtained from the sale was used to buy new shares of American Airlines, another affected airline. Regarding American Airlines, it was found that the sale of shares came from investors who had received by post a newsletter from a financial analysis company advising to sell these shares because a particular forecast that they had on the the stock market. And for the shares of the affected insurance and banks companies, there was a similar explanation, nothing that connected with the 9/11 attacks.
• As it often happens with international events, anti-Semitic theories emerged suggesting that Jews were behind the September 11 attacks to cause chaos and through helding positions in the media, banks, military industry and government, have a chance 'to control the world'. Initially, these theories claimed that the Israeli intelligence services alerted Jews not to go to work to the Twin Towers that day as they knew what was going to happen. After identifying most of the victims, however, it was found that more than 300 Jews died at the World Trade Center, a higher percentage of deaths than the Jewish population that normally is found in Manhattan on a normal working day. Israel is in permanent conflict with several Arab countries, but there is no indication that there could have been a reason why it would have caused this event at this particular date.
In the case of Saudi Arabia, there is evidence from independent sources and the US government that prove a connection with the 9/11 attacks. At the request of the victims' relatives, Biden finally ordered the release of these documents. On them, it is shown with material evidence that members of the Saudi Arabia government and their Embassy in Washington D.C collaborated directly with the terrorists in the planning of hijacking the planes. Saudi Arabia, which is a brutal Islamist dictatorship, is indeed an increasingly uncomfortable ally for the US government towards the public opinion.