People will fucking believe anything!
First of all people, simple physics. Mass x acceleration = Force. A jumbo jet airliner, fully loaded with crew, passengers and fuel weighing approximately 200,000lbs flying at about Mach .50 or .60 (approximately 415mph) that crashes into the outer ring of a building that was A) first built to withstand direct aerial bombarbment and provide as much protection as possible from a
nuclear attack and B) had just undergone a massive remodeling project in the section that was struck to reinforce the building against new types of missiles/bombs/and bunker-pentrating weapons.
Secondly. Newton's Laws. All of them. Inertia, Equal and Opposite Forces, etc.
Third. Go look at photos of Flight 93 and see just how much actual airplane debris you can locate in that crash site. Once again, simple physics.
Fourth. How many people have actually heard a missile in this country? Sure we have had heard them LAUNCHED, but have you ever heard them in-flight? I would bet my life that less than .01% of the population of the U.S. has ever been in that situation. The simple fact of the matter is missiles are propelled by ROCKET engines not JET engines. You wouldn't be able to hear the missile in-flight til it was well past your location because missiles travel at HYPERSONIC speeds and what you're hearing is the sonic boom that is BEHIND the flight path of the missile.
Fifth. I have lived near a commercial airport, Will Rogers World Airport and a military airbase, Altus Air Force Base. I have heard plenty of commercial airliner takeoff/landings as well as plenty of C-5, C-135 takeoffs/landings. A jet engine has a very high-pitched sound as it accelerates or gears down for landing. Now it's pretty safe to assume that the people intent on crashing the plane into the building weren't gearing down for a landing but they were accelerating. And you'll remember again from physics that acceleration is not only a change in speend but also a change in direction. And as someone else mentioned earlier, the Doppler Effect comes into play with regards to sound. An object's pitch is going to change as it approaches a set point as the sound waves become compressed and frequency intensifies, and the pitch will change again as the object moves away from said point as sound waves decompress and spread out.
Sixth. I guess the families of those that boarded the flight that struck the Pentagon made up the stories about never seeing or hearing their families members ever again. Oh wait, I know, the government shot down the plane over a remote location and covered that up too.
Seventh. I guess the communications recordings that I've heard for more than 4 years now between flight contollers and the planes were made up too.
Eighth. I offer you this website with plenty of photos for you to look through. Take particular notice of the damaged taxi cab on the interstate that was crossed as well as the damaged light. Oh also notice how about 80 feet or so of the E-Ring of the Pentagon is missing. Oh wait, that's only a 6 foot hole isn't it? Oh and how about the exit hole in the C-Ring or the damage to the D-Ring as well as the C-Ring?
http://images.google.com/imgres?img.../images?q=Pentagon*attack*&svnum=10&hl=en&lr=
Just remember, it's all a conspiracy involving tens of thousands of individuals.
EDIT: Hell, I almost forgot about the debris of the airplane lying there in the grass with the familiar silver paint scheme with the red stripe...Where have I seen that before....Oh ya, it's the paint scheme for American Airlines!!