Pilot sighting of UFO SAUCER while flying in a Citabria aircraft

Date : June 20,1987  Time : 12:15 p.m.
Location : Near Cedar Point, Ontario, Canada  
Flying in my Citabria aircraft at 3500 ft. a.s.l., the UFO saucer was sited south east of Christian Island as I was banking my aircraft to the right on a level turn. I opened my left side window to watch as the UFO passed approximately 500 ft. underneath my plane (this distance is only an estimate on my part). I then banked the plane to the left so that I would not lose sight of the saucer as it when under the nose of my aircraft.
 The UFO continued on a straight and level path, and although my air speed was 110 m.p,h. the UFOs speed was such that there was no way I could catch up to it. If I had to approximate it's speed, I would guess at 400-600 m.p.h. The saucer never deviated from it's straight course.
 As for the size of the UFO, I can't really say, since there was nothing that I could compare it to. But if I had to guess, I would say about 30 to 50 feet in diameter. It happened so quickly, but I did get a very good look at it. There were no windows or any markings on the UFO saucer. The colour was a dull silver, almost a grey colour.
 I usually carry a camera in the side carrying pouch by the pilot's door. But this time, the camera was in a sports bag behind the rear passenger seat. There was no way of getting access to the camera. If I had a passenger with me that could have handed me the camera, I would have been able to get a very good picture with my 35mm camera! Now when I go flying, I always make sure that I have at least two cameras with me at all times. This was a once in a life time experience.
 It is now 20 years since I had my UFO encounter. To this day, I have had no other experiences with UFO sightings from the ground or in the air.