silver disc shaped object flying extremely fast at a low altitudeI was having breakfast with my wife at a local restaurant. Our table was located right next to a large picture window, facing North at the end of Main Street. As I looked out, I noticed a small Cessna airplane flying slowly on its final approach to the Bismarck airport. Just as I was losing sight of the Cessna, I looked back to my right and spotted a silver metallic object flying extremely fast in a straight line from East to West. The object appeared to be disk shaped, similar to a double-convex lens if looked at from a side view. The object was approximately 1/4 mile to the North and appeared to be flying at a lower altitude than the Cessna had been, I estimate about 300 to 400 feet above ground level. I believe the airplane would have been moving at about 80 knots, therefore, I would estimate the disk shaped object was moving at between 500 and 700 mph, as I lost sight of it within 2-3 seconds. The object appeared to be a little smaller than the airplane, approximately 18 feet in diameter.I am an amateur radio operator and trained weather spotter. I have taken fixed wing flying lessons and have built and flown R.C. model aircraft for many years. I am familiar with most types of aircraft and I have seen anything in the sky like this before.((NUFORC Note: We spoke via telephone whith this witness, and we found him to be exceptionally lucid and eloquent. We suspect that he is an excellent witness. PD))