Will post more on this, but just as a preface I'll say that most people figure the "whitish object" in the video is what struck the building (as Straw Man and I did earlier in the thread). But it appears that "whitish object" is something trailing the plane and being emitted by it, actually.
To give a better idea, here are stills released by the Pentagon. What you see on the left sticking up above the box, is said to be the tail. So when the FBI makes the claim about lack of a relevant image, they are referring to all things which have been unreleased.

There is so much more to this. I have heard 80 cameras, 100+ cameras. I don't think 80 cameras were aimed in such a way that they had that particular area of the pentagon in their view. Even if some did, we are dealing with a very fast moving plane on a very low resolution with a very slow frame rate. That's probably the best one available. The whitish object is said to be a smoke trail from the engines.
For those who believe a missile hit the pentagon.
Absence of a clear video of a plane hitting the pentagon doesn't prove a missile hit it.
However, absence of evidence (such as eye witnesses of a missile) suggesting a missile hit the pentagon and the plane and passengers were somehow disposed of, proves that a missile didn't hit the pentagon and the plane and passengers weren't disposed of.
Additionally, there is plenty of evidence, in the form of witnesses, records, photographs, after math accounts, debris, documented defense system failures etc. that suggests a the plane did hit the pentagon.
This is why the whole missile thing is loony.