Not seen that video before.
It's too hard to tell if it's a plane or missile.
It looks to small to be a plane / wings don't look long enough.
Though at the speed it's traveling at & quality of the video who knows.
I still find it difficult to Believe a fairly inexperienced pilot could reduce the flying height
To such a very low / only feet above the ground & not make contact with the ground
& also find a completely clear route into the pentagon without hitting anything.
Perhaps he had practised this route & manoeuvre several times before.
Certainly a skilful bit of flying.
Not wondering why you haven't seen it before? Because it is fake, that's why. Quite simple reason, isn't it? You see it from the "stop motion" quality of the picture, which is also turned around (youtube logo is backwards), so if you are smart enough to wonder why in the name of god someone would use stop-motion camera while filming from the airplane, you realize it is ridiculous, so it has to be fake. In fact this has to be a fake made to prove how foil hat morons accept any kind of fake information as truth, if it fit's in their prejudices. Furthermore, if it would be 5 meters long cruise missile, you wouldn't see it at all, because it is so tiny compared the building. And why, oh why you guys think that a crap like this would overrule all those evidences which proves it was a 757? This is the part which is most difficult to understand? If someone show you this kind of badly faked video, how it would overrule all the eyewitnesses who saw the 757, not a little tiny missile? Are you proving just now that you haven't seen the passenger jet at close distance never in your life? You see, if something like 757 fly past you at the dive speed, it would be a vision you never forget. I have seen plenty of low level flyby's and it is always a remarkable experience, but suddenly at the front of the pentagon it doesn't mean anything to people who see it? For real? Are you some kind of moron by any chance?
Here is the original version where you see clearly that the "missile" is edited in the pictures afterwards by some incompetent fool: