13 conspiracy theories about the 9/11 terror attacks that destroyed the Twin Towers

On September 11, 2001, 19 hijackers flew planes into the twin towers of World World Trade Center in Manhattan, New York. A third plane crashed into the Pentagon, and a fourth intended for the US Capitol crashed into a field. Nearly 3,000 people were killed, in what was one of the rarest and certainly the worst terrorist attack on American soil.

The United States administration blamed terror outfit Al Qaeda and its leader Osama bin Laden for the attacks following an investigation. Subsequently, the US declared war on Afghanistan, which set off a chain of conflicts in the Middle East.

9/11, as the date came to be called, changed geopolitical equations forever. Over the 14 years since, the scourge of Islamist terrorism has become global, and the West is engaged in seemingly endless wars in much of the Middle East.

However, not everyone around the world believes that the 9/11 attacks were carried out by Al Qaeda, and without the knowledge of US administration or intelligence. Several conspiracy theories have floated around, with scientific phenomena often being used to justify them.

1) The Twin Towers collapsed as a result of controlled demolition, not the impact of the planes: One theory states that the World Trade Center towers collapsed because explosives had been planted inside them. Physicist Steven E Jones, architect Richard Gage, software engineer Jim Hoffman, and theologian David Ray Griffin are some of the proponents of this theory. They contained that the structure of the towers could not have been weakened enough by the impact of planes, and the resulting fire from jet fuel. Jones went so far as to suggest that government authorities might have used thermite or super thermite to ensure the collapse of the buildings. The fact that both buildings fell in vertical fashion, as if being pulled into the ground, was used as further justification for this theory.

2) Israeli agents caused the terror attack: It has been claimed that Israeli secret agents were involved in the collapse of the towers. Five hours after the attacks, the FBI arrested five Israelis who had been filming the smoking skyline from the roof of a white van in the parking lot of an apartment building, for "puzzling behavior". It was concluded that these two men were Israeli intelligence operatives.

3) Pentagon hit by a missile: Some conspiracy theorists have argued that the Pentagon was not damaged as a result of the crash of American Airlines Flight 77. Instead, a missile was dropped on it. One popular conspiracy theory website claims that the holes in the Pentagon walls were far too small to have been made by a Boeing 757.

4) Plane shot down by US air force: It is claimed that the United Airlines Flight 93, which crashed in a field near Pennsylvania, was actually shot down by a US fighter jet. Some plane debris were found several miles away in Indian lake. It is contended that a mere crash could have caused the debris to dissipate over such a long distance.

5) Fake passports and visas: While the 9/11 Commission determined that 16 of the 19 hijackers did not carry valid documents to enter the United States, it is alleged that a conspiracy at the highest levels of US government allowed them across the border. This is used as proof that the US government wanted the attacks to be carried out.

6) Pretext to attack Middle Eastern countries: Some people state that the 9/11 attacks were staged so that the US and its allies could launch military campaigns against Middle Eastern countries. The 'terror attack' was used as an excuse to justify these campaigns. The 'Zionist conspiracy' angle, which seems to crop up every time there is a terrorist attack in the West, is also tied to this theory. The 2003 US invasion of Iraq, which was founded on a debunked claim that the country held weapons of mass destruction, has sometimes been used as further proof that the US wished to declare war on certain countries. The group Scholars for 9/11 Truth argued that a group of US neo-conservatives the likes of Paul Wolfowitz and Dick Cheney wanted to resume US domination of the world following the end of the Cold War, and hence planned the attacks.

7) No planes were used at all: This is the most bizarre theory of all. Former official under the Bush administration, Morgan Reynolds claimed that no planes had been used in the 9/11 attacks. Instead, a technique knows as digital compositing was used to make missiles appear like planes in videos of the attacks. This theory though has been debunked even by most conspiracy theorists themselves.

8) The Illuminati carried out 9/11: Some 9/11 truthers claim that the Illuminati, a global secret society that seeks to create a New World Order under a totalitarian world government, planned and carried out the attacks with the help of some of the world's governments.

9) US air defence was asked to 'stand down' prior to the attacks: Some truthers allege that the  North American Aerospace Defence Command (NORAD), which is tasked with shooting down misbehaving airplanes, asked US defence systems to 'stand down' in order to enable the attacks. The lack of response of these systems to four planes flying low in US airspace is often cited as proof for this theory.

10) The hijackers were alive after the attacks: Immediately following 9/11, the BBC published the names and identities of some of the alleged hijackers. Some of the names corresponded with those of living people from the Middle East. Some 9/11 conspiracy theorists believed this to be evidence that the US was not attacked by Islamists from the Middle East. The BBC clarified that some of the names were fairly common in Arab countries and thus it could have been a case of mistaken identity. But some passports belonging to the alleged hijackers were found after the incident, adding fuel to the fire.

11) Inside traders knew 9/11 would happen: It is alleged that an extraordinary amount of put options were placed on United Airlines and American Airlines stocks, the same airlines that were hijacked during the attacks - just a few days before the attacks took place. Many speculate that insider traders on the US stock markets were tipped off about the attacks in advance. It is true that many made big profits from the tragedy. 

12) Black boxes were concealed by US intelligence: Conspiracy theorists claim that the FBI concealed vital evidence - black boxes found from the sites of the attacks. The 9/11 Commission states that only two black boxes were found instead of four. But Michael Bellone and Nicholas DeMasi, who worked extensively in the wreckage of the World Trade Center, claim they helped FBI agents recover three black boxes. The 9/11 Commission on the other hand states in its report that of the two black boxes found, one was too badly damaged to be of any use. Only the CVR from Flight 93 was intact. On April 18, 2002, the FBI allowed the families of victims from Flight 93 to listen to the voice recordings.

13) Bin Laden tapes were fabricated: It is alleged that the interviews and videos of Osama bin Laden following 9/11 are fake. In December 2011, Laden denied he was responsible for the attacks. Some 'experts' claimed that the translations of Laden's tapes were fabricated, and that the original tapes did not call for a terror attack at all. In 2007 Bin Laden claimed responsibility for the attacks, but stated that the Taliban in Afghanistan had no idea about them. This was contrary to the analyses of intelligence agencies and experts in the West who deciphered that the Taliban did in fact have some knowledge of the attacks.

Over the years, most of these conspiracy theories have been met with ridicule, derision or even outrage. The United States and its allies have presented various kinds of evidence to debunk these theories.

Incredibly, the idea that a cover up was involved finds credence with a significant percentage of the US population even today. A 2008 opinion poll by WorldOpinionPoll.org showed that globally, people were divided on who they believed carried out the attacks. While some believed that Al Qaeda indeed was responsible, many others felt that the US government itself planned the attacks. Some respondents blamed the attacks on Israel.

Other polls, including those by leading agencies like PEW Research showed that only a small minority of Muslims felt that Al Qaeda or 'Arabs' were responsible for 9/11.

However, it is to be noted that the official theory (that Al Qaeda planned and executed 9/11) finds favour mostly in countries which are US allies, while the Israeli and US government conspiracy angles are largely embraced by countries hostile to Israel and/or the US.