http://en.wikipedia.org/?title=9/11_conspiracy_theories9/11 conspiracy theories attribute the planning and execution of the September 11, 2001 attacks against the United States to parties other than, or in addition to, al-Qaeda[1] or claim there was advance knowledge of the attacks among high-level government officials.[2] Government investigations and independent reviews have found no evidence for the theories.[3][4] Proponents of these conspiracy theories claim there are inconsistencies in the official conclusions, or evidence which was either ignored or overlooked.[5]
The most prominent conspiracy theory is that the collapse of the Twin Towers and 7 World Trade Center were the result of a controlled demolition rather than structural failure due to impact and fire.[6][7] Another prominent belief is that the Pentagon was hit by a missile launched by elements from inside the U.S. government[8][9] or that a commercial airliner was allowed to do so via an effective stand-down of the American military.[10][11] Possible motives claimed by conspiracy theorists for such actions include justifying the invasions of Afghanistan and Iraq (even though the U.S. government admitted Iraq was not involved in the attacks)[12] to advance their geostrategic interests, such as plans to construct a natural gas pipeline through Afghanistan.[13] Other conspiracy theories revolve around authorities having advance knowledge of the attacks and deliberately ignoring or assisting the attackers.[5][14][15]
The National Institute of Standards and Technology (NIST) and the technology magazine Popular Mechanics have investigated and rejected the claims made by 9/11 conspiracy theories.[16][17] The civil engineering community accepts 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.[18][19] This also was the conclusion of the 9/11 Commission, chaired by Governor Thomas Kean.
