UFO? Or Advertising device?

Back in 1976-77, I was in fourth grade and living in a rural part of town. I remember sitting on my bed one evening as dusk was nearing, looking out my window. I saw a strange object come into view. It appeared to be a small UFO and it flew close to my house and then out to the horizon before turning around and flying back close to my roof. There were lights all around the middle.
The strangest part was that there were words lit up in the middle of the object, kind of like a reader board. It read "You are doomed to die..."
Being about 9 years old, that kind of freaked me out a bit. But as I said, it came back again, and this time it read, "Skippy Peanut Butter $1.79" or some such price.
I realized it might be some kind of advertising device, but I still don't know what it was. I've never heard or seen anything like it since, nor has anyone that I have asked.