My wife and I were driving between Alpine and Fort Davis, Texas after a short vacation. I glanced out my driver side window and saw an white colored object in a clear blue sky. I asked my wife if she could see the object and she concurred. I then pulled over on the rural highway and we watched it hover for at least ten minutes until we decided to head on with our trip. I took several photos with a digital camera but they didn't come out that good. There was no sound and no discernible movement. After driving off we watched it and could tell with the changing perspective that it could have been four to six miles away from our location and that it was enormous. between 100-300 feet in length. We lost sight after driving on through the Davis Mountains.