White, large arrow-shaped UFO flew over/near Las Vegas airport on a November evening.It was 7PM on a November Friday night. It was clear and cool. It was dark. My 13-year old son had just come to join me in the backyard hot tub. I was looking at him and talking as he stepped down into the tub. As he sat down, he exposed the sky above him and I saw the UFO.The UFO was at a 25 degree elevation to me, about 1 - 3 miles away, as I looked SSE. The UFO was headed due south. It appeared to be right over the Las Vegas (McCarran) airport. It was about the size of a dime held at arm's length. It was white, and shaped like a full-bodied arrow on a street sign. The stem of the arrow was only as long as the arrow head was wide. It produced a brief white tail behind itself, the full height of the arrow.The UFO was going dangerously fast if it was over the airport. It moved at 3 to 6 times the speed of the airliners I constantly see in that area.I watched it for 20 seconds. I stammered for my son to look, so he observed the flight for 10 seconds. As it flew south, my view was soon going to be blocked by my second story roof line. Just as I was about to lose my line of sight, the UFO just vanished out of sight in an instant. I heard no unusual noises that evening.