Nearly the same thing happened to me back the late 80"s or early 90's, i'm standing in my yard after dark and happened to notice a large triangular shaped craft drifting right over my house and didn't make any noise at all. I watched it go way out to the eastern horizon and then it suddenly pulled a 180 back towards me before going down and disappeared below the horizon. I think it was an alien spacecraft because nothing made by man with our current technological advancement can perform that type of aerial maneuver and not make any noise.