salo_t, as I wrote earlier, the image from that security camera is worthless. And you see “that stuff” at other crash sites because the plane is usually not traveling at 500mph in other crashes. Most airliner crashes have been during takeoff or landing when speeds are lower and angle of approach is smaller. In that Pentagon crash you had a heavy jet moving 500mph slamming head-on into a wall. The energy difference is huge vs. an airliner on takeoff or landing at 150mph crashing at a shallow angle into the ground. This was not a typical airliner crash at all, which is why there’s not a lot of debris, most of it disintegrated and burned. And as to why it penetrated so far into the building, it was a large, heavy object carrying a tremendous amount of kinetic energy; it had to go somewhere.
