Me and my Brother-in-law were driving N/NE on I75 S to his "Core Buyer" in Detroit,Mi. I Was looking as usual for them all the time because we have seen them in the past on the Interstate. When I seen it and pointed it out to him and we immediatly knew what it was. Remarkably fast and huge. In comparison to its height,length and distance in the air compared to an airplane was 10/1 in size. It switched direction as if thrown into reverse at a high rate of speed.planes were in the area so We had something to compare it to.When moving side to side it appeared cigar/shiny and reflective;like light but could see some grey in it. but apperared like a clear,blurry round sphere shape before we last seen it and wondered if it was even the same one.we thaught maybe it was its underside we seen and the cigar shape was maybe the side view or something. It was partly cloudy and the speed could be measured by how fast it went past a airplane in the sky and how fast it passed the clouds from one break in them to another. like they were manuevering in between the cloud cover. "TRUST ME;IT WAS A UFO" Please keep in mind that I have a witness; one that is just as fascinated with space and ufo's as I am. I hope this information helps you.