White ball of light accompanied passenger jet (above the plane, then slightly ahead, then disappeared).My Husband and I were sitting still in a boat on Lake Chelan with a bright blue clear sky above. We looked up to see a passenger plane flying probably 20,000 feet heading north. What was odd, was the white ball above it -- half the size of the plane and moving exactly the same speed. By the time I grabbed the binoculars, the ball was closer to the cockpit, but then they were both too far to really see clearly. The ball disappeared after about 4 minutes.