A lot of people think that the ace elevator company was involved. They were supposed to be doing work to upgrade the elevator system. It was supposed to be globally one of the biggest ever upgrade projects given the size of the buildings. The job gave them access to the core of the buildings where explosives could have be planted. The company ceased trading after 9/11.

With regards to asbestos removal it was only done on a certain number of floors. If I recall the total cost of removal of the asbestos from entire buildings was supposed to have been a billion dollars, more than the cost of a new buildings. Luckily for Mr silverstein both buildings killed themselves.