Definitely an aircraft but totally silent and very slow.Driving home from work and stopped for a pit stop Horsethief roadside rest along Rock Creek. Standing in an open area surrounded by aspens when object appeared just sightly above tree top level I'd say approx 50 ft. At the time I said to myself "holy ((deleted))" I'm seeing a ufo. Then I realized the craft had regular aircraft lighting. What was weird was the craft was absolutely silent and traveling at about the speed of a car on a residential street 35mph. I was an air traffic controller for six years both radar and tower, and for some reason I just wrote it off as some new military technology. It was traveling east to west and I watched it go slowly out of sight. In this area there is a radar range where aircraft rotinely practice terrain avoidance flights. I had seen quite a few other aircraft practicing this procedure in this area as the B52's used to do when I was stationed in ME.((NUFORC Note: Time and date are approximate. PD))