In a sheet responding to FAQs they published in 2006, NIST gave a brief
rationale for avoiding the important issue of controlled demolition in the
studies of the collapse of the World Trade Center Towers, which they concluded
were brought down by the plane impacts and subsequent fire. They avoided
mentioning Building 7, another World Trade Center building that collapsed but
without any impact from a plane. The facts, which NIST claimed
justified their failure to investigate that issue for the towers, are
challenged as being incorrect. The evidence for and implications of the issue
of controlled demolition of the towers are addressed.
The National Institute of Standards and Technology (NIST) released a publication of answers to frequently-asked-questions (FAQs) on August 30, 2006. One of those questions dealt in part with the issue of controlled demolition, an issue many engineers, physicists and other scientists have put forth evidence for in the collapse of all 3 buildings at the World Trade Center on 9/11/01 (e.g. see ,,,,,). This other part of the same question dealt with the "pancake theory" of collapse from fires. This was an unusual mixture of issues into a single question, as there is strong evidence for controlled demolition causing the collapses instead of fires from the planes in the references cited, but virtually none for the pancake theory of collapse from fires created by the planes. Here is the part of the question on controlled demolitions as NIST formulated it and the answer they provided to it.
Q: Why did NIST not consider a controlled demolition hypothesis with matching computer modeling and explanation...? A key critique of NISTs work lies in the ... lack of consideration given to a controlled demolition hypothesis.
A: [After 4 paragraphs on all the work NIST did and why they did not support a pancake theory] NISTs findings also do not support the controlled demolition theory since there is conclusive evidence that:
* the collapse was initiated in the impact and fire floors of the WTC towers and nowhere else, and;
* the time it took for the collapse to initiate (56 minutes for WTC2 and 102 minutes for WTC 1) was dictated by (1) the extent of damage caused by the aircraft impact, and (2) the time it took for the fires to reach critical locations and weaken the structure to the point that the towers could not resist the tremendous energy released by the downward movement of the massive top section of the building at and above the fire and impact floors.
Video evidence also showed unambiguously that the collapse progressed from the top to the bottom, and there was no evidence (collected by NIST, or by the New York Police Department, the Port Authority Police Department or the Fire Department of New York) of any blast or explosions in the region below the impact and fire floors as the top building sections (including and above the 98th floor in WTC 1 and the 82nd floor in WTC 2) began their downward movement upon collapse initiation.
In summary, 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.
I directly challenge the accuracy of the facts claimed in this answer that NIST has formulated. There are 3 types of errors in this answer.
1. The collapse was not initiated in the fire and impact zone in the South Tower as NIST claims! It was clearly initiated below that zone, as squibs [material shooting horizontally at high velocities] burst through the walls of the tower below the impact & fire zone. This was clearly in floors that had not been affected by the fires. Photos of these initial stages of collapse from  with 2 separate cases of squibs bursting through walls below the floors with the plane impacts and the fires they created, are shown in Figs. 1, 2 and 3. These squibs are moving material with significant kinetic energy and momentum, and are evidently generated by explosions inside the tower (the only feasible source of this kinetic energy and momentum). The explosion driving the first set of squibs that initiated the collapse caused a noticeable leaning of the top segment of the tower, and the explosion driving the second set of squibs twisting that top segment like a bottlecap. Under no circumstances can these squibs with their significant quantities of energy and momentum come from the previous plane impacts or the fires they created.
Figure 1. The South Tower when the collapse first starts, in which multiple squibs have appeared from floors below the fires. Note that the top 34-floor segment of the tower has developed a lean to the left and into the page, as seen on the right corner front face. The squibs are evidence for explosions below that top segment, the only feasible source of the kinetic energy and momentum of the squibs breaking through the walls.
Figure 2. South tower 0.5 secs after Figure 1, in which the squibs have expanded over 30 feet outside of their ejection region. Their rapid velocity shows the squibs have significant kinetic energy and momentum generated from that explosion. Note that the leaning of the top tower has increased from Figure 1, which indicates part of the energy of that explosion has gone into moving that top segment (34 floors).
Figure 3. Photo 1.5 seconds after Fig. 2, in which a new set of squibs have ejected out on 2 different floors below the plane impact zone. With those squibs the top tower segment makes a major turn counterclockwise, indicating it acquires a significant piece of angular momentum from these squibs. The top of the top segment has moved down significantly from Fig. 2 indicating it is substantial undergoing disintegration at it bottom, which is just above the floors in these 3 figures from which squibs are emerging. The gray clouds are coming from the disintegration of the segment where the plane fires were, while the white clouds are coming from the disintegration of the floors below where the fire was located.
2. The claim that "... there was no evidence of any blast or explosions in the region below the impact and fire floors as the top building sections (including and above the 98th floor in WTC 1 and the 82nd floor in WTC 2)..." most clearly disagrees with the evidence for both towers! Both the North and South Tower showed clear evidence of multiple blasts below the fire zone with horizontal squib ejections bursting at high velocities through the walls of the towers. For the South Tower these are as described in  and shown in Figs. 1, 2 and 3, while in the North Tower there were repeated squib ejections out multiple walls from several different floors of the tower below the fire zone.
Photographs with examples from the North Tower of these ejection below the plane impact zones, and below the level of material falling from the collapse are shown in Fig. 4 and 5. They show ejections through the walls on multiple floors and in multiple directions, which can only be driven by explosive forces from inside the tower. Note one of the ejections shown in Fig. 5 is an unusually long solid object which has not all come out, so that its right side but not its left is falling due to gravity.
Figure 4. The collapse in the North Tower less than 1 second after it starts, which clearly shows rapidly expanding dust clouds , a sudden leaning of the top antenna based on the core, a flash of light on the right-side showing an explosion outside the tower, and a squib ejecting through the walls out the tower on the right-hand side, rougly 10 floors below the lowest plane-impact region and the dust clouds. The squib ejection is driven by a separate explosion inside the building at that level below the level of the fires and plane impacts.
Figure 5. North Tower collapse less than 2 seconds later, which shows the right-hand side of the top ejected squib is falling due to gravity. It shows that ejection was a solid long object, with the left-hand side not completely out the building and resting in the vicinity of the wall it broke through. There is also ejections several floors below that, both on the right-hand side and on the front face (coming toward us), which may both the driven by the same explosion inside the tower.
3. There is an abundance of other direct evidence of explosions. This includes broken pieces of cladding, beams, and sections of wall flying away from the tower in the collapse (see Figure 6), as well as directional impact damage on around 1400 cars in the vicinity of the World Trade Center at the time the building collapsed. The evidence of this damage is abundant, and could not have been produced if fires from the planes caused the collapse.
Figure 6. The collapse less than 1 second later, which shows that a blown-off 6-story piece of the wall (over 3000 ft2 in size) is falling on the left, and the 30-feet steel beam ejected (see Fig. 5) is falling on the right. The steel beam has flipped over so that its front end is nearest the tower, and that front has been buckled from its high speed collision (driven by explosive forces) with the wall upon its exit out the tower. There are hundreds of other pieces of beams and other objects emerging from the dust cloud in the collapse. All of these phenomena provide strong evidence for production by explosions.
In summary, NIST's claim that they "found no corroborating evidence...
suggesting that the WTC towers were brought down by controlled demolition"
strong suggests that they did not even begin to look at the issue. The
evidence is clearly there in References  thru  for the twin towers,
in Figures 1 thru 3 from the article focusing particularly on the South Tower
collapse , in Figures 4 thru 6 specifically for the North Tower ,
and in the hundreds of cars hit directionally with damaging material
up to 1000 feet or more away from the towers (shown in ). They show that
NIST's conclusion that planes brought the towers down are completely in error.
 Frank Legge, "9/11 - Evidence for Controlled Demolition," Journal of 911 Studies, Volume 1, June, 2006. Posted at http://www.Journalof911Studies.com/articles/ Journal_2_Evidence_for_demolition_20.pdf
 Gordon Ross, "How the Towers were Demolished," Journal of 911 Studies, Volume 2, July, 2006. Posted at http://Gordonssite.tripod.com/id2.html
 Stephen Jones, "Why Indeed Did the World Trade Center Buildings Completely Collapse?" Journal of 911 Studies, Volume 3, September, 2006. Posted at http://www.Journalof911Studies.comvolume/200609/Why_Indeed_Did_the_WTC_ Buildings_Completely_Collapse_Jones_Thermite_World_Trade_Center.pdf
 Tony Szamboti, "The Sustainibility of the Controlled Demolition Hypothesis for the Destruction of the Twin Towers," Journal of 911 Studies, Volume 11, May, 2007. Posted at http://www.Journalof911Studies.com/Volume/200704/SzambotiSustainabilityof ControlledDemolitionHypothesisforDestructionofTwinTowers.pdf
 Crockett Grabbe, "Direct Evidence for Explosions at the World Trade Center," Journal of 911 Studies, August, 2007. Posted at http://www.Journalof911Studies.com/Volume/200704/GrabbeExplosionsEvidence.pdf
 Crockett Grabbe, "Collapse of the South Tower of the World Trade Center," submitted to Journal of 911 Studies, October, 2007. Posted at http://www.SeaLane.org/writings/STcollapse.html (Photos of South Tower collapse linked to 911 Research videos.)
 Excellent photos of the collapse of the North Tower were taken by Richard Lethin, posted at http://www.reservoir.com/extra/wtc/index.html
 Morgan Reynolds & Judy Wood, "Toasted cars" section, posted at http://drjudywood.com/articles/DEW/StarWarsBeam5.html NOTE: These were presented as evidence for beam weapon destruction at the towers, but  discusses how energetic squib impacts from the towers provide a much better model for their creation on 911. This NIST conclusions about the towers falling from fires created by the plane impacts cannot explain them -- they effectively help prove that conclusion is wrong.
Check out SeaLane.org/speak