If you look at the place it hits the bulding, in comparison the to the position of the object entering from the right you can quite clearly see that the object is travelling at right angles to the camera. Its coming straight at the pentagon. So i dont think its a wing tip. If it was then the object would have hit the camera prior to the pentagon.
Lord knows - it is security camera footage after all
If the plane came in at an oblique angle as claimed then what you can see could just as easily be wing tip.