A 3 billion lbs steel building was leveled by a 200,000 lbs aluminum plane and and it’s fuel...? Keep in mind these buildings had 200,000 metric tons of steel. That’s 4,409,000 lbs of steel.
That’s some damn impressive payload for a 200,000lbs aluminum vessel.
I’m going to help you out here, just a lil’bit......
Kinetic energy transfer of a plane weighing almost 400,000lbs(not 200,000lbs as You mentioned) traveling 350-400 mph is approximately 2723790Joules, which is a very significant impact. The initial impact alone could have cut through the steel support columns and brought the building down.
Liken it to this analogy, have you ever heard of a piece of straw impaling a tree trunk during a tornado? So you can’t say aluminum can’t do damage.