Few scientists are willing to vouch for the official 9/11 conspiracy theory. Well, sure, there are a few Benedict Arnolds on the government payroll, either directly or via defense contractor, who will use their credentials to deceive.
But, there is no chorus of independent experts championing the government's conjectures (which are sold to the public as "fact" even though the reports themselves are careful to note that the official scenarios are really guesses). After all, how can credible experts assess the official theories? All that can be said is "insufficient data" because a pile of evidence that would affirm or debunk government claims is still under lock and key, despite numerous FOIA efforts.
No serious scientist is going to back a government scenario knowing that critical data is being withheld.
On the other hand, there is a growing group of professors who do have competence to sift evidence who are unconvinced by the government's official theories.
Who is willing to back up the official stories? Popular Mechanics, a little Hearst organization mag that keeps track of the latest technical widgets, is about the best the government can do. Then there was a columnist for Scientific American who challenged those who don't believe the government (Shermer is a Skeptic, but not of the government). Yet, I recall seeing no piece by a scientist writing for that popular magazine affirming the government theories.
In fact, there hasn't exactly been a glut of articles in technical or scientific journals affirming government theories, and not many scientists speaking out publicly in favor of government scenarios. Those who do are usually psychologists who tend to think that conspiracies are mostly paranoid fantasies. (I guess they think "it can't happen here," which is what Jews in Hitler's prewar Germany thought.)
On the other hand, the professional organizations that should be speaking out against the government are hunkered down and grotesquely silent.
Today I heard a snip of a radio discussion between the producers of "Loose Change," which focuses on apparent inconsistencies in the government line and Popular Mechanics journalists who said that all the "myths" have non-conspiracy explanations. The most important point is that Popular Mechanics seemed eager to deflate balloons rather than do an honest story that, while perhaps puncturing myths, also takes note of discrepancies and inconsistencies.
I haven't read the Popular Mechanics debunker book, but I read the magazine article, and all I can say is that it was a typical bit of Hearst sleight-of-hand of the type the Hearst press used in the JFK assassination coverup.