My wife, son and I was outside on our deck enjoying an evening outside. I was facing North, my wife was facing South and our son was facing West. There were no clouds in the sky, anywhere. I happened to look up and saw about a dozen "streaks" ( like you see in Star Trek shows where they go into hyperspace). They were from the South headed true North. I said, Look! At that moment a triangle UFO appeared and stopped I believe, between the Salt Lake International Airport and Downtown Salt Lake City. The UFO was huge, about 400' to 500' per side and between 4 and 5 stories high. It was silver in color with rounded edges. It had three large, super bright white lights that were circular on the bottom of the craft. It also had three rectangle blue lights, also underneath, that were along each side of the triangle. The white circular lights were towards the middle of the craft. It stayed stopped for approximately one second. It then went almost straight up toward the North West at an unbelievable speed an disappeared in a split second. My son saw it stopped and take off, however my wife wasn't quick enough to turn around, to see it. The UFO made no sounds whatsoever.