Image:Wtc arial march2001.jpg|thumb|The collapse of the two World Trade Center towers and the nearby WTC7 (in this photo, the brown building to the left of the towers) is a major focus of 9/11 conspiracy theories. 9/11 conspiracy theories allege that the September 11 attacks in 2001 were either intentionally allowed to happen or were a false flag operation orchestrated by an organization with elements inside the United States government. The most prominent theory is that the collapse of the World Trade Center and 7 World Trade Center were the result of a controlled demolition rather than structural weakening due to fire. Another prominent belief is that the Pentagon was hit by a missile launched by elements from inside the U.S. government The commonly claimed motives are to justify the invasion of Afghanistan and Iraq, leading to subsequent US control of their vast oil resources; to facilitate increased military spending; and to restrict domestic civil liberties. Published reports and articles by the U.S. National Institute of Standards and Technology, Popular Mechanics and mainstream media have rejected the 9/11 conspiracy theories. The majority of civil engineers state that the impacts of jet aircraft at high speeds in combination with subsequent fires, rather than controlled demolition, led to the collapse of the Twin Towers and WTC 7.

[Last contributor : Rich Farmbrough , Content under LGPL licence]