Nononononono.... if they were going to create a conspiracy
they would have just flown the plane into the fucking building
Assuming it's a conspiracy, there's 2 options:
1)They disappeared the passengers and the plane and fire a missile or something into the pentagon... which is pointless and can be traced back to them. Note that this option also requires more thought so the "because they're idiots" argument can't be used.
2) They just fly the plane into the pentagon then
say the terrorists did it.
Come on, if you were a conspirator, which one would YOU choose?