If you watch the sequence of photos, the object is falling like a parabola which is consistent with projectile physics. It came from the second crash. The red line is a red herring. Break out the Heavy Duty Renolds Wrap.
That would be a reasonable explanation, except that when you watch the video clip the object first appears ABOVE the explosion of the second plane (you have to look carefully to see it against the dark background of the first column of smoke).
Based on the speed of this "projectile" (even in slow-motion) and the fact that it is way out of focus, I would say that something flew in front of the camera while the video was rolling.