DX, good pick on movies! Got a bit more information you might find interesting in regards to it: The punch it gave to the pentagon (four sets of steel reenforced 32 inch thick walls) is a match to the prototype cavebuster missile(built to ram through up to 38 inches of solid stone; modified to 56 inches of penetration); the manuverability shown, its invisblity to radar and the precision of the blast(no external scorching to the ground and none to items within the blast zone) support the concept.
I also want to point out the lack of debris at the towers...