There are people who really believe that a 757 didn't hit the Pentagon based upon their huge mistrust of the U.S. government.
If you are convinced, as you should be, that 9/11 was an inside job to some degree, but believe real, common, un-bought people have testified truthfully that they saw the 575 flying at the Pentagon, then don't fret about the no-plane promoters. Just keep saying that there are numerous named and recorded witnesses of diverse backgrounds and political ideologies who say otherwise — who say they saw the 575. (See: "9/11 and the Pentagon Attack: What Eyewitnesses Described," Arabesque: 9/11 Truth. April 2, 2007.)
9/11 and the Pentagon Attack: What Witnesses Described)
There are so many really solid questions and evidence surrounding 9/11 that a thorough investigation would turn up proof beyond a shadow of a doubt that officials within the highest ranks of the U.S. government were directly involved in the false-flag operation, just as the U.S. ran Operation Gladio in Europe.
They can't take Operation Gladio back. Operation Gladio was a huge false-flag operation that is an admitted false-flag operation of the CIA. Their cover was blown. Their pattern of behavior is known. 9/11 fits that pattern, as do Pearl Harbor and many other events, like the Gulf of Tonkin for one among many. It's the same with the assassinations of the Kennedys and Martin Luther King, Jr.
No amount of trying to focus upon a plane or no-plane hitting the Pentagon will alter all the evidence on that day.
So what if the FBI ends up releasing video from all the CCTV (closed-circuit TV) cameras that captured images of what hit the Pentagon? If an American Airlines 757 ends up being clearly shown to the world, it won't answer any of the other questions. It won't refute the known facts about 9/11.
Until the whole day and every lead leading up to it and every lead thereafter is properly followed the way a really well trained and experienced criminal detective would, there are going to be plenty of untrained, inexperienced people speculating.
So what if the CIA and others manage to get some people to wonder one way or the other about things? They cannot stop the 9/11 demand for a thorough investigation. 9/11 isn't 12/7/1941. The people who bought the official version of Pearl Harbor were not networked as people are today. There was no Internet where publishing is as easy as posting a blog post.
9/11 will not be put to rest until a real investigation. The government of the U.S. will never enjoy "legitimacy" again until it turns from being the instrument of global capitalist plutocracy. That's just the way it is. The sooner everyone comes to realize it the better.