The collapse of the Twin Towers and 7 World Tra

de he result of controlled demolitions rather than structural

failure due to impact and fire. Another prominent belief is that was hit by a missile launched by elem

ents from

inside the U.S. government or that a co

mmercial airliner was allow an effective stand-down of the American military. Possible motives claimed by conspiracy theorists for such actions include justifying the invasions of Afghanistan and Iraq (even though the U.

S. government concluded Iraq was not involved in to advance their geostrategic interests, su

ch as plans to co

nstruct a natural gas pipeline through Afghanista conspiracy theories revolve around auth

rities havi

ng advance knowledge of the attacks ag or assisting the attackers.

The National Institute of Standards and T

echnology (NIST) and the techno

logy magazine P

opular Mechanics have investigated and rejected the claims made by 9/11 conspiracy theorists. The 9/

11 Commission and most of the civil engineering community accept that the imp

acts of jet ai

rcraft at high speeds in  hon combination with subseq

uent fires, not controlled demolition, led to the collapse of the Twin Towers, but some groups disagree w

ith the arguments made

y NIST and Popular Mechanics, including Architects & Engineers for 9/11 Truth.