Driving. I saw a huge white blimp looking thing out the window. That was my initial thought, of course. It remained hovering. It was just under the clouds, but there were only a few clouds in the sky. It was against the blue. It was completely feature less. I pointed it out to my brother. Then we watched in confusion as it disappeared over the horizon at unbelievable speeds. It was almost above me and almost gone in five seconds.