“I know an eye witness who was getting off a tour bus at the Washington Monument that watched the plane fly into the Pentagon”.
I’m not doubting your eyewitness, but perhaps they thought they saw a plane? (Loose Change, YouTube)
We can "see" things not there and miss things that were there. There's a video about basket ball players with a man in a gorilla suit walking through the midst of them. It's shocking how many people to not "see" the man in the gorilla suit. They have to see it again before they'll believe he was there.
Did they just imagine pulling this hub from a Boeing 757 main landing gear wheel from the inside the Pentagon?
Or this combustion chamber ring from a Rolls Royce RB211-535E4B triple-shaft turbofan engine. It is the proper size and configuration for that part as numerous aircraft engineers and mechanics have attested.
How about these nose landing gear wheels and gear struts, the heaviest parts of the plane in the nose, found at the furthest extent of the damage in the A-E Alley where they still had enough momentum to go through the wall into the alley?
Then there are the pieces of the American Airlines Boeing 757 fuselage littered across the lawn where it was scraping the ground before it hit, leaving pieces showing the AA livery.
And finally, this part, which not only has the AA of American Airlines on it, but also has a serial number traceable to the airframe of the particular Boeing 757 used for Flight 77 that day.