A plane hitting an exterior steel frame building would only damage the side that was hit. At the very most, the part of the building above that would crumple and tip over. There's no way in the world that would cause the entire building to drop straight down into it's own footprint.

A bomber flew into the Empire State Building a long time ago, and it just stuck. There was no explosion or anything but local damage. The plane was hoisted down, the building was repaired, and life went on.

Collapsing three of the strongest skyscrapers in existence with two "planes" is just total BS. The buildings were professionally demolished.