World Trade Center controlled demolition conspiracy theories

Some conspiracy theories contend that the collapse of the World Trade Center was caused not solely by the airliner crash damage that occurred as part of the September 11 attacks and the resulting fire damage but also by explosives installed in the buildings in advance. Controlled demolition theories make up a major component of 9/11 conspiracy theories.

Early advocates such as physicist Steven E. Jones, architect Richard Gage, software engineer Jim Hoffman, and theologian David Ray Griffin proposed that the aircraft impacts and resulting fires themselves alone could not have weakened the buildings sufficiently to initiate the catastrophic collapse and that the buildings would have neither collapsed completely nor at the speeds they did without additional energy involved to weaken their structures.

The National Institute of Standards and Technology (NIST) and the magazine Popular Mechanics examined and rejected these theories. Specialists in structural mechanics and structural engineering accept the model of a fire-induced, gravity-driven collapse of the World Trade Center buildings, an explanation that does not involve the use of explosives. NIST "found no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives planted prior to Sept. 11, 2001." Professors Zdeněk Bažant of Northwestern University, Thomas Eagar of the Massachusetts Institute of Technology, and James Quintiere of the University of Maryland have also dismissed the controlled-demolition conspiracy theory.

In 2006, Jones suggested that thermite or super-thermite may have been used by government insiders with access to such materials and to the buildings themselves to demolish the buildings. In April 2009, Jones, Dane Niels H. Harrit and seven other authors published a paper in The Open Chemical Physics Journal, causing the editor, Prof. Marie-Paule Pileni, to resign as she accused the publisher of printing it without her knowledge; this article was titled Active Thermitic Material Discovered in Dust from the 9/11 World Trade Center Catastrophe, and stated that they had found evidence of nano-thermite in samples of the dust that was produced during the collapse of the World Trade Center towers.