On September 11, 2001, a group of Al-Qaida terrorists hijacked four planes and crashed two of the aircraft - United Airlines Flight 175 and American Airlines Flight 11 into the twin tower of the World Trade Center. They crashed American Airlines Flight 77 into the Pentagon, and the fourth plane crashed into a field in Pittsburgh, Pennsylvania after a struggle between the hijackers and passengers. The 9/11 terror attacks shook the entire world. Today marks 18 years since the deadly strike on the world's most powerful country. 9/11 Quotes & Sayings: Heartfelt Memorial Messages to Remember Victims of September 11 Attacks in the United States.

As many as 2,977 people died in the 9/11 terror attacks. Though Al-Qaeda claimed the responsibility of one of the most dreadful attacks of the 20th century, many still don't rule out 'inside job'. According to a poll conducted by the BBC, one in four 16- to 24-year-old thinks the US government was involved in a conspiracy to stage 9/11 attacks. On 9/11 Anniversary State Michael Pompeo, Says Terrorism is a Global Issue.

9/11: Marking The 18th Anniversary Of The Terror Attacks That Irrevocably Changed U.S. History:

Here are some of the most compelling conspiracy theories floating around:

What Led To The Collapse Of WTC towers?

The most well-known conspiracy theory relates to the collapse of the twin tower of the World Trade Centre and WTC 7. The 47-storey WTC 7 collapsed seven hours after the two towers fell. Conspiracy theorists allege that explosives were planted at the WTC twin tower and Tower 7, and demolitions were controlled. They believe the crash and subsequent fires didn't lead to the collapse of towers. However, the National Commission on Terrorist Attacks Upon the United States, also known as the 9/11 Commission, accepted that the impacts of jet aircraft at high speeds in combination with subsequent fires, not controlled demolition, led to the collapse of the Twin Towers.

Jews Knew About 9/11 Attacks

Conspiracy theorists also allege that Jewish and Israeli workers and occupants knew about the 9/11 attack and were warned the day before, supposedly by the Mossad (the Israeli intelligence agency) to stay away. One of the most widely circulated claims is that not a single Jew had been killed in the 9/11 attacks. Similarly, some claim that all Arab taxi drivers were absent in downtown Manhattan that morning.

On September 17, the Lebanese Hezbollah-owned satellite television channel Al-Manar claimed that 4,000 Israelis who worked at the World Trade Center “remarkably did not show up in their jobs”. However, this was a false claim. According to an article in the Wall Street Journal published on October 11, 2001, roughly 1,700 people had listed the religion of a person missing in the WTC attacks; approximately 10 per cent were Jewish. Catch more details here - The 4,000 Jews Rumor.

No Planes Theory

Morgan O Reynolds, who is the former director of the Criminal Justice Center at the National Center for Policy Analysis, claimed that no planes were used in the 9/11 attacks. Reynolds claims it is physically impossible that the United Airlines Flight 175 and American Airlines Flight 11 could have penetrated the steel frames of the WTC towers. David Shayler, a former Mi6 officer, said: "the only explanation is that they were missiles surrounded by holograms made to look like planes". However, plane wreckages were recovered. Multiple witnesses also saw the plane strike the Pentagon.

(The above story first appeared on LatestLY on Sep 11, 2019 11:07 AM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).