One of the questions immediately after the 9/11 attacks was whether or not Osama bin Laden realized that he might be able to bring down the World Trade Center Towers with passenger jets.
CNN has a story which quotes from a video featuring bin Laden that was apparently released last November, though this is the first time I remember this particular quote being mentioned,
“Due to my experience in this field, I was thinking that the fire from the gas in the plane would melt the iron structure of the building and collapse the area where the plane hit and all the floors above it only. This is all we had hoped for,” bin Laden said on the tape.
So, apparently bin Laden hadn’t realized that by collapsing the floors above the impact zone that he could bring down the entire tower.