Having looked into 911 for many years I'm now leaning towards Directed Energy Weapons (DEW's) and 'No-Plane' theory as the most likely hypothesis. The subject is given a thorough treatment by Dr. Judy Wood at this link....Star Wars Directed-Energy Weapons (DEW)
Another researcher who has done stirling work in this field is Andrew Johnson. Heres a book he wrote:
9-11 - Finding the Truth by Andrew Johnson PDF
We can no longer rely on mainline 911 'truthers' for correct info. It seems that the movement has been infiltrated from day 1 by the likes of Steven 'Los Alamos' Jones and possibly others.
Good introductory video here:
More discussion on this on our forum thread :911 Inside Job