Object traveling at speed faster than conventional aircraft, white in color, brief metallic color noticed.

Object appeared in a blink of an eye and traveled for about 20 seconds horizontal to the ground at a slower speed but then shot off at a high rate of speed that is faster than any known aircraft that I know of. The sky was clear, the object was white in color but I also saw a brief moment of metallic color as well. Object had a fuzzy area around it's edge. The object was like an egg shape and then stretched out flat like. There were no flashing lights seen on the object. It then became the shape of an egg again and disappeared. Altitude was possibly between 25 to 40 thousand feet. There was no contrail to indicate it as a conventional aircraft. Within the time of my observation, the object went from large to small then it was gone. There were no obstructions within the line of sight of the object. No clouds, trees or mountains. Although meteor showers happening during this time period, I don't think it was a meteor because it had no trail behind it and it slowed down at one point in time during my observation.