I believe the Pentagon is a highly secure US government building?
Surely this building would have been built with re-inforced concrete, steel support columns and a whole host of impact designed materials, its not
like your average office block, I have seen the results of a small 'terrorist' bomb on a building in London where I lived, it left scorch marks and
nothing else a good jet washer would have removed all traces on this device.
Video clip of an F4 being crashed into a wall (at roughly 500mph), it disintigrates there is virtually no 'identifable' remains left.
So even if a larger aircraft had smashed into the Pentagon the same results would apply, the building would have been built to withstand large impacts
with relatively no damage and due to the integral strength of the building it would have pulverised the plane on impact.
A Boeing 747-400 fully loaded with 216,389 liters (57,164 gallons) of fuel
The fuel can burn at 2050c at its highest flame temperature
Other materials burn at:-
Aluminium 660c (a majority of a plane is made from this)
Steel 1370c (if the structure is strengthen with this material it explain why the structure remain so stable)
Copper 1083c (wiring for the plane)
Plastics 250c (coating on wires other items, seats, plastic interior)
UK crematurions have to operate at a temperature of 850c, for you know what.
I think that this would have 'liquidated' alot of the ingredients that make up a plane.
Flying a plane into a target, look at the towers, they were pretty precise. Don't know if it still on the market, Microsoft Flight Simulator was
apparently quite exacting on its controls and the handling of a plane and it was rumoured that they used this software to practise. Follow Formula One
motor racing? several drivers practice on virtual driving games to learn the tracks (Jenson Button UK driver) Its not hard if you are commited to do
something this henious and do it right first time.
All things are relative, you crash your car in to a 2 ft solid re-inforced concrete wall at 80mph whats going to happen, okay now do this with a plane
that manages to break though the first wall, but then hits a second, then a third, then a fourth? After the first and second the engines are probably
still on full power combine this with the kinetic energy already in the plane, its gone.