Demartini, who had an office on the 88th floor of the North Tower, has been missing since the 9/11/01 attack, having remained in the North Tower to assist in the evacuation.

This is from Dr. Steven Jones:

I also agree with Kevin Ryan’s objections regarding the NIST study.  Kevin Ryan, at the time a manager at Underwriters Laboratories (UL), makes a point of the non-collapse of actual WTC-based models in his letter to Frank Gayle of NIST:

As I'm sure you know, the company I work for certified the steel components used in the construction of the WTC buildings. In requesting information from both our CEO and Fire Protection business manager last year… they suggested we all be patient and understand that UL was working with your team… I'm aware of UL's attempts to help, including performing tests on models of the floor assemblies.  But the results of these tests… indicate that the buildings should have easily withstood the thermal stress caused by… burning [jet fuel, paper, etc.].  (Ryan, 2004)

That models of WTC trusses at Underwriter Laboratories (UL) subjected to fires did NOT fail is also admitted in the final NIST report:

NIST contracted with Underwriters Laboratories, Inc. to conduct tests to obtain information on the fire endurance of trusses like those in the WTC towers…. All four test specimens sustained the maximum design load for approximately 2 hours without collapsing… The Investigation Team was cautious about using these results directly in the formulation of collapse hypotheses. In addition to the scaling issues raised by the test results, the fires in the towers on September 11, and the resulting exposure of the floor systems, were substantially different from the conditions in the test furnaces. Nonetheless, the [empirical test] results established that this type of assembly was capable of sustaining a large gravity load, without collapsing, for a substantial period of time relative to the duration of the fires in any given location on September 11.  (NIST, 2005, p. 141; emphasis added.) 

So how does the NIST team justify the WTC collapses, when actual models fail to collapse and there are zero examples of fire-caused high-rise collapses?  Easy, NIST concocted computer-generated hypotheticals for very “severe” cases, called cases B and D  (NIST, 2005, pp. 124-138).  Of course, the details are rather hidden to us.  And they omit consideration of the complete, rapid and symmetrical nature of the collapses.

Indeed, NIST makes the startling admission in a footnote on page 80 of their Final Report: 

The focus of the Investigation was on the sequence of events from the instant of aircraft impact to the initiation of collapse for each tower. For brevity in this report, this sequence is referred to as the "probable collapse sequence," although it does not actually include the structural behavior of the tower after the conditions for collapse initiation were reached...(NIST, 2005, p. 80, fn. 12; emphasis added.)

Please read the entire paper by Jones here:

http://physics911.net/stevenjones.htm