Why 9/11 wasnt an inside job

He wasn't alone in asking questions. Sections of the official US government report were redacted for years - and some information is still missing. However that doesn't mean there's any evidence for the more outlandish online conspiracy theories about the attacks.

Some claim the US government was complicit - that officials deliberately let the attacks happen or were even involved in the planning. Experts say part of the reason for the persistence of such conspiracy theories is the dissonance that results when people hear that a relatively small group of men using low-tech weapons caused such cataclysmic carnage. And the reinforcing nature of the online world means that the theories have hung around for a decade and a half. People tend to share it with people who kind of think the same way as they do about these issues in the first place," she says.

The theories have been propelled by several books and films. David Ray Griffin, a professor of religious philosophy and theology, accused the US government of complicity in the attack in his book The New Pearl Harbour.

The first instalment in filmmaker Dylan Avery's Loose Change series was released in It was so widely available, a digital copy was even later found in Osama Bin Laden's compound. The confusion and chaos of 11 September has also helped the conspiracies find an audience. This tower has become a key focus for people who question the official account of what happened.

A storey building about metres from the twin towers, WTC7 was never struck by an airplane. Two planes plus three towers has equalled plenty of questions - questions compounded by the BBC's own reporting of the collapse of WTC7. In the frenetic, confusing aftermath of the terror attacks, the BBC reported that WTC7 had collapsed twenty minutes before the building actually came down.

In , the BBC's The Editors blog addressed the reports and traced how an on-air comment about an imminent collapse turned into reporting about the building actually falling - shortly before WTC7 did indeed fall. Any apparent discrepancy was cleared up by a report by the National Institute of Standards and Technology NIST which found that WTC7 collapsed after fires on multiple floors "caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down".

But that did not change the minds of the conspiracy theorists. His organisation has raised hundreds of thousands of dollars to fund additional research at the University of Alaska Fairbanks. The conclusions of that study will be published in Matt Campbell's also still looking for answers.

He called the trial "a bit of a farce" but said: "It's the closest I'm ever going to get to a trial into the murder of my brother. Some online conspiracy theories suggest US missiles were fired at the Pentagon, as part of a government plot, and the hole left in the building was too small to have been caused by a passenger plane. But a member of the American Society of Civil Engineers told Popular Mechanics magazine the size and shape of the hole was due to one wing of the Boeing hitting the ground and the other being severed on impact with the building.

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. It was fire that caused this. And the fire is believed to have come from the burning of remaining aircraft fuel. According to the FEMA report, fire within the buildings caused thermal expansion of the floors in a horizontal and outwards direction, pushing against the rigid steel columns — which deflected to an extent but resisted further movement.

With the columns resisting movement, there was nowhere else for the concrete floors to expand to. This led to an increased buildup of stress in the sagging floors, until the floor framing and connections gave in. The collapsing floors then fell on more floors below, leading to a progressive collapse.

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.