About that impact/entry hole: It just looked small because of the telephoto shot. But, wing tip to wing tip, it reached at least 10 floors of the building(s) because of the 30 degree or so angle the plane hit at. The wing span of the planes was something over 100 feet and bin laden had coached his guys to be in a turn on impact so that they reached as many floors as possible. The impact hole was the cross section size of the plane(s) measured at the fuel tanks.
If those planes had been empty they would have wadded up like an empty beer can hitting a cowboy’s forehead and done very little damage to the building.
But the planes had nearly a full load of fuel and that’s what did the damage. At high speed a tank full of any liquid might just as well be concrete. The hydraulic effect of initial impact is pretty much like a brick in a window. As the tanks begin to shred, tho, the fuel vaporizes and it’s all downhill from there.
If you look closely at the initial impact holes they look more like the shape of the fuel tanks than the actual shape of the plane. The people inside the planes, being organic, would have contributed a bit to the “dieseling” effect of the impact. Diesel engines use 18to 1 compression ratio. Hitting a solid wall at 400 mph would be around 100 times that, so, yeah, they dieseled.
Interesting information. The plane vaporized but something made it through to make the punch out hole on the other side.