Lead is too narrow 
The lead states "Adherents of the 9/11 Truth Movement deny that al-Qaeda terrorists hijacked four airliners and intentionally crashed two into the World Trade Center buildings". I think this is too specific, as not all proponents argue this. Some (engineers particularly) only claim that the towers were brought down with the help of explosives without any assumptions as to who was involved. The use of explosives doesn't preclude Al-Qaeda (or anyone else) from hijacking (or otherwise) airliners (or aircraft of similar description) from intentionally crashing into the WTC. It seems fairly obvious that aircraft flew into the buildings, but that also doesn't preclude the use of explosives. I'm not a die hard truther, but I don't belive the mainstream media or the US government either. As a structural engineer there does seem to be some quirks in the hypothesis put forward by NIST, and the apparent hasty destruction of material evidence from the disaster does seem very questionable. Calling for further investigation doesn't seem unreasonable regardless of what actually happened. There seems to be a lot of people who get offended even by the mere suggestion of further investigation (which may in fact help to clear the government of any involvement). I guess these people (who seem to get all their 'facts' from Fox and CNN) explain why the US government is able to get away with gradual erosion of liberties (PATRIOT, NDAA, TSA, etc). Ignorance must surely be bliss for these morons. Goodbye ye olde 'land of the free and the home of the brave'.