Noticed a bright white light moving across the sky in the north/northwest sky of Las Vegas, Nevada. It appeared high in the sky. It was moving slowly. It would then stop for a minute or two at a time and stay stationary, then move again. It was partly cloudy and it appeared that sometimes it would maneuver to get into or more clear area of the sky. In its maneuvers to re-position, it would move in very short, extremely fast speeds. This having appeared so to me, at its seemingly high altitude the speed there must have been tremendously fast. I watched for approximately an hour, after which it became faint and I could not see it anymore