This whole cruise missile argument is so absurd that many of the 9/11 conspiracy theorists themself has given up on it as too bizarre. Even the makers of Loose Change discount it at one point when they claim an A3 Skywarrior hit the Pentagon, but since people keep proposing this theory I will address it one more time.
The filmmakers (at this point) claim:
So what could blow a 16 foot hole in the outer ring of the Pentagon, smash through 9 feet of steel reinforced concrete and leave another 16 foot hole? A cruise missile. This is what Slobodan Milosevic's residence in Belgrade looked like after a Tomahawk cruise missile had hit it. See any similarities?
What the filmmakers are leaving out is that this is all the damage to Slobo's place. The missile didn't continue and blow up the next house two blocks away.
Cruise missiles are relatively small, lightweight unmanned flying planes, with engines not much bigger than the V-8 on my Mustang. They hit their target with precision and blow up, leaving everything within a few dozen yards on every side pretty much trashed. They don't knock a 90 foot hole in a concrete wall, and then continue 310 feet through the world's largest office building. They don't have the inertia.
Physics. The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force.
Most of a cruise missile is the warhead, after the warhead and fuel explode, there is not enough force to push the remaining couple of hundred pounds of engine, aluminum and carbon fiber 300 more feet through 2 more rings of the pentagon.
270,000 lbs of 757 travelling at 500 MPH. Now that has inertia.