Walked out on patio which I have a due west vision and looked up and seen five very bright lights soccer ball size in a straight vertical pattern equaldistant from each other.My view is about 10 miles from the start of the mountains. I live about 40 miles from Denver airport.The sky was black so I could not make out any shape but the lights.I watched the a andlights travel in a straight line over the mountains getting smaller as they got farther away until they were out of sight.Total time was 10 t0 15 minutes.Much slowe than a commercial airliner with no running lights.I watach the sky every day and nights for various periods and have yet to see anything like this before.