A Boeing 757 did not hit the Pentagon
by Michael Meyer, Mechanical Engineer
I am a Mechanical Engineer who spent many years in Aerospace, including structural design, and in the design, and use of shaped charge explosives (like those that would be used in missile warheads).
The structural design of a large aircraft like a 757 is based around managing the structural loads of a pressurized vessel, the cabin, to near-atmospheric conditions while at the lower pressure region of cruising altitudes, and to handle the structural and aerodynamic loads of the wings, control surfaces, and the fuel load. It is made as light as possible, and is certainly not made to handle impact loads of any kind.
If a 757 were to strike a reinforced concrete wall, the energy from the speed and weight of the aircraft will be transferred, in part into the wall, and to the structural failure of the aircraft. It is not too far of an analogy as if you had an empty aluminum can, traveling at high speed hitting a reinforced concrete wall. The aluminum can would crumple (the proper engineering term is buckle) and, depending on the structural integrity of the wall, crack, crumble or fail completely. The wall failure would not be a neat little hole, as the energy of the impact would be spread throughout the wall by the reinforcing steel.
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