Silent black rectangle flying over highway Augusta, GA

I was driving to work this morning traveling west on I-20.  It was about 5:45 and it was still dark, but the sky was a monarch blue color before the sunrise, so it was not completely dark. I was between Washington Rd and Bobby Jones exits when I saw a dark shape in the sky flying at about 2 o'clock to the right of my car.  It zig-zagged and started coming toward the highway. I thought...wow! That is a huge bird!...and by the time that it got over the highway, I thought that it might be a helicopter, but it had no tail and no propellers.  It had no lights and was completely silent. It got close enough for me to tell that it was black and looked like a rectangular pod of some sort and definitely mechanical-looking. I could see side pipes and what might look like vents on it.  Although it was difficult to tell just how high it was, it was not too high...as I looked to the left over my shoulder as I saw it go across me over the highway, it looked like it just skirted the tree line before it disappeared.  I was not scared, but had a car behind me and I did have to be careful, because I did not want to run my car off the road.  If it was a plane or a helicopter, it would have had lights.  Due to the low altitude, if it had been either of those, I would have heard it.