People are not sure it was a plane that hit the pentagon...

[ziggytrix]

According to the internet, the typical operating weight of an EMPTY Boeing 757 is 64105 kg. It's approach speed is 263 km/h.

The force it takes to stop a 757 at approach speed would be 4683226 Newtons for each second it took to stop. Assumming it stoped moving from impact to rest in 10 seconds, that's 468323N or 105283.2 pounds force.

The 757 that crashed into the Pentagon was actually travelling much faster, about 560 km/h, but I don't feel like redoing the math - we're talking about a force of over a hundred tons.

With a 20 x 20 foot fuselage, that's roughly 190 TONS per square inch of impact surface. And that's not even counting the force of the explosion of the fuel.