"If it wasn't a plane, or even the plane they said it was, tell me where the passengers and said plane are right now."
Add to that, that no one has any reason to assume that, based on what they saw, a plane didn't hit the Pentagon when they don't know what a plane of that size crashing into the Pentagon, at that speed and, with a large amount of fuel on board is supposed to look like to begin with.
"I always thought that crash site looked suspicious. Where the heck is the plane?
Why was there no footage?"
There wasn't much wreckage at the site of Flight 93 either (IIRC). Not much footage either.