I saw something around 1988

It was my only sighting, where I saw something very clearly. I was living in Pennsylvania at the time. I saw it up it the daytime sky flying in once direction. It made no sound, and stayed on a straight course all the way to the horizon. It appeared to be round, and was gray or silver in color. Only time I had a really good sighting, the rest were just some dot in the night sky, flying around all crazily