After much reading and studying it is obvious that NIST, FEMA and the 9/11 Commission have all fallen short of a detailed accounting of the catastrophic collapses of the three World Trade Center buildings in Manhattan on 9/11/01. A few examples of unexplained details include the "severe high temperature corrosion attack on the steel" as described in Appendix C of the FEMA Building Performance Study, the complete symmetrical collapses following asymmetric structural damage and short-term fires, and the chemical signature of incendiary compounds found in the toxic WTC dust.
I would really like to know why complete collapse of the twin towers "became inevitable" as expressed by NIST without any scientific analysis to substantiate it. Why would all 110 stories drop straight down to the ground in about 10 seconds, pulverizing most of the contents into dust and ash - twice? Why would WTC 7 fall straight down to the ground in about seven seconds the same day? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified - and necessary - for all three collapses.