I stepped outside our backdoor at approximately 9 p.m. and noticed a very bright light flash in the southern sky at 30 or 40 degrees. At first I thought it was my imagination but kept eyes focused in the general area. Then it flashed again and the light diminished in intensity until it was invisible. It was traveling North about the speed of a plane but with the exception of the bright flash, there were no navigational lights that I could determine. The strange part of it was the pattern of flight. It seemed to be traveling in a straight line but would suddenly appear off to the left as if it had made a sharp turn. Sighting only lasted less then 2 minutes until it finally disappeared from view. There was no sound at all. I would estimate the height to be about 20,000 to 30,000 ft.