The problem here is the possible levels of government involvement. I'm willing to accept that 9/11 went down exactly as we saw it happen - the real conspiracy may have been behind the scenes. For example, maybe some terrorists did actually plan the whole thing and some people in high up positions of the US intel world (it wouldn't take many...) made sure it happened......hence NORAD pretty much standing down or being bogged down in some exercises that morning, which coincidentally involved hijacked planes crashing into buildings. In which case it would be almost impossible to prove. And then it could be any level of involvement above that - including some things that may seem far-fetched.