http://en.wikipedia.org/wiki/9/11_conspiracy_theories
"9/11 conspiracy theories attribute the planning and execution of the September 11 attacks to parties other than, or in addition to, al-Qaeda[1] or claim there was advanced knowledge of the attacks among high-level government officials.[2] Government investigations and independent scientific reviews have found no evidence for the theories. Proponents of these conspiracy theories claim there are inconsistencies in the official conclusions, or evidence which was overlooked.[3]
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.[4][5] Another prominent belief is that the Pentagon was hit by a missile launched by elements from inside the U.S. government[6][7] or that a commercial airliner was allowed to do so via an effective stand-down of the American military.[8][9] Possible motives claimed by conspiracy theorists for such actions include justifying the invasions of Afghanistan and Iraq as well as geostrategic interests in the Mideast, such as pipeline plans launched in the early 1990s by Unocal and other oil companies.[10] Other conspiracy theories revolve around authorities having advance knowledge of the attacks and deliberately ignoring or assisting the attackers.[3][11][12]
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.[13][14] 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.[15] This also was the conclusion of the 9/11 Commission, chaired by Governor Thomas Kean"
Read on. The article covers the ground.
