I have always believed that many buildings were rigged for controlled demolition before 911. The reason I feel was that there was intelligence of this type of attack , but nothing specific. I do not believe that grounding all airlines was ever an option and so measures were taken so that if an attack of this sort were to occur it would be possible as a last resort to prevent one of these buildings falling sideways and taking out half of New York.This is just a theory but if true I have nothing but sympathy for anyone touched by this diabolical attack. P.