Abruptly maneuvering black object hovers over Ventura County, CA, displaces cloud formations 12/06/02Single dark/black object that changed shape from a disc to an ovoid as it moved. Object moved south over Ventura County, California at 16:10 to 16:13 at approximately 10-15,000 altitude, then the object hovered in one area from 16:13 to 16:18. During hover object made several unusually tight (seemingly) uncontrolled maneuvers, and this is when the object changed shape from a disc to an ovoid. After maneuvering over Ventura County area, object abruptly changed course toward the north and continued north until it was out of sight (from 16:20 to 16:25). As the object moved, it displaced cloud formations in a circular area surrounding it--the area directly around the object was clear even when flying through cloud formations.Observers: 1) Male 43 Professor at local college. 2) Female 50 Artist/Art instructor at local college.