Massive black triangle - spotlight on each corner - moving very slow at treetop height

I've seen a number of interviews of Lou Elizondo, and it is fascinating to hear credible people speaking about the UFO topic. It has me frequently thinking about a strange experience that I had when I was 16.
I was with my friend Adam driving in the late evening somewhere in the Rockford area, away from town and surrounded by fields, patches of trees and scattered homes. I don't remember the exact location.
We were passing a very large farm field on the left side of the car that had a patch of trees on the far end. We saw three large spotlights just above the tree line. As we approached, we realized that this was an enormous black triangular object, like 100 yards long. There were lights on each corner. The object was an elongated triangle. It was hovering and traveling forward slowly, maybe 100 - 200 feet above ground at most and traveling the opposite direction of us with its lights pointing on the field in front of it. It was way too large to be an airplane or helicopter. It was moving way too slow to stay up in the air if it was a conventional fixed wing aircraft. It was completely silent. There was no wind in general, but also no turbulence caused by the object - grass, trees - nothing.
We couldn't wrap our heads around what we saw and were so scared the we drove by it at I'm guessing around 35 mph (we definitely slowed down from the 55 mph that we were going, but were also too terrified to stop). We only told a few friends about it, as it seemed so ridiculous that we expected most people would not believe us.
The part that shocked me most was that the idea of a triangle shaped UFO was completely foreign to me at the time. I thought UFO meant "flying saucer". A few months later, I was at a friend's house. There was a coffee table book about UFO's laying around. I started flipping through it and just about fell out of my chair when I saw a photo of exactly what I saw. I've seen other images of a black triangle, but the three lights are usually on the bottom, inset from the edges and shining directly down. The lights were on the corners, oriented both down and forward (like a headlight aimed way down), and were super bright.