Starsgirl,
firstly, the planes that hit the two towers were Boeing 767-200ERs and it will not be such an easy task to prove that these buildings fell due to the impact of these two planes. The evidence strongly posses facts that the impact of a 767 could not have caused the complete structural failure of either building causing the four hundred thousand tons of concrete to completely pulverize and fall unhindered to the ground at near free-fall speed. The amount of energy contained in one of the exploding aircraft was not nearly sufficient to create and even greater destructive force than what energy had already been applied. Energy released is proportional to the energy applied and there is no way to prove the towers fell as a result of aircraft impact. It did not happen that way!
Google AE911 Truth and you will find a treasure trove of facts from literally thousands of engineering experts that totally disprove the faulty NIST report concerning the destruction of the World Trade Center...you may find the evidence frightening and disturbing...
Good luck with your essay...it will be easier to prove the opposite...planes did not cause the towers to fall.
James...