I was driving down the highway and saw a bright flashing white light flying our way. I slowed down to look at it. I had a passenger with me. The aircraft had a triangle front; the flashing light was on the tip of the triangle. Connected to the triangle were straight sides. So it was all one piece, triangle top and rectangle back. From the road we were looking up at it and it looked flat. It was almost 10p.m. so it was dark out and when the light would rythmically flash on and off, we could see it. It was flying at a slow speed going north along the highway. We were heading south. It was on our left side. When the light would flash it looked steel grey with cross "bars" and panels that looked like square windows. There were 2 or 3 "window panels" on each side with the "bars" between. It looked like there were thin green lines of light, straight lines outlining part of it. It was flying in the direction of the front light. We didn't stop and kept going. My passenger turned to watch it continue on its path. It was flying above the power lines, a little bit higher. We didn't know what it was. I was very interested in what it was but as we were driving to our destination and this probably only lasted a minute or two I didn't stop. I didn't have much time to think about it. My passenger felt scared of it and didn't want to stop. We have no idea what it was. It was nothing like what we've ever seen before. My drawing is obviously not as good as in person but it just gives an idea of what it was like. I called the Missouri university science and technology center to see if they had any experiments going or whatever and the night watchwoman said they didn't. I tried to call Fort Leonard Wood Military Base but that was not working out. So I wanted to report this and ended up here.