Watch the video of the second plane hitting. It hit near a corner. A big fireball erupted outside of the building. That’s jet fuel which is not burning inside causing the steel to soften. Things that make you go hhhmmmm?
Both buildings pancaked straight down. They didn’t fall sideways into another building. It looked more like a controlled demolition. I would be inclined to think that jet fuel would create uneven heating within the floors, creating a collapse towards the weakest portion first. In that case, the building would not collapse straight down, but would’ve fallen sideways.