UFO - 13 miles over Area 51 FULL VERSION filmed by U.S. Military camera.

This UFO seems to change shape as the video progresses, it looks cylindrical, like a rocket at first, them seems to change into a Mushroom shape then has strange 'exhaust' ports protruding?

Anyone know any factual information about this video clip, I have seen it around but not this FULL VERSION before.

The pilots haven't got a clue what it is, neither does ground control, very interesting clip.