Jourles is right, the images are too blurry and ambiguous to be of much help. The first video shows something that is probably bigger than a missile (taking the lens' foreshortening of objects into account) but which doesn't quite look like the forward section of an airliner either (motion blur?). The second video shows something that looks very much like a tailfin at 0:26 (which would be inconsistant with a missile) but it has what looks like a smoke trail which doen't fit with the profile of a plane in flight. The lack of contrast in the dark background doesn't help either. BTW, the video does not show the plane hitting the ground; the ground was completely intact in the area shown in the video (the plane, rather, collided with five lamp posts on the roadside and objects on the lawn near the building, see the ASCE report). I think the visualization by Mike Wilson gives the best explanation thus far of the apparent smoke in the video....the starboard engine was possibly damaged by lamp post debris from one of the two poles it struck:
http://www.youtube.com/watch?v=YVDdjLQkUV8
The physical evidence from the scene (the five knocked-down poles, the structure on the lawn with a wall on the side, the chain-link fence and the generator behind it, the damage to the Pentagon wall, the aircraft debris on the lawn and in the building, passenger remains) otherwise indicate what struck the building.