Ok, I went and watched the whole thing. First of all, holy crap! That's a hell of an explosion! Now as far as the object... I see your point about apparent speed for an object at some distance, but I'm now thinking it's maybe a bug, but much closer to the camera. I think the object passes on the close side of the towers, although trying to pause it at that instance was too tough for me. Now, if you look at the 4:10 mark, you see a similar object zoom from left to right. It looks a bit different, but you get a sense of speed because of how close it is. If it were a mile away, it would be breaking the sound barrier. Like I said, I wish it was an alien craft!! :-)