Watching sunset on computer shortly after cigar shape appears

I was watching the sunset on my computer of Spearfish S Dakota weather cam, shortly after sunset a cigar shape appears it was metallic and moved slowly from left to right on my screen. My husband and I watched until it got to the end of my screen. I was able to back up and watch again that's when I started to video and take pictures. There were no flashing lights like a plane would have, in fact no lights at all. This took place at 9:15 central standard time that's my time. I believe that Spearfish is an hour behind us.