I was in the front picture window of my parents' house. I was 18 years old. It was raining with grey full cloud cover over the sky and lightning.

My viewing was North towards the hill of Nose Hill Park watching the lighting.
The airport is East of this location approximately 6 Kilometres.
A big lighting strike occurred above the hill when a UFO appeared approximately three Kilometres.  It was huge, at least two commercial airliners put together.  Most of the UFO was Dark grey that tapered into a dome shaped top.  The dome had colours in it including red and green.  In the middle, you could see a band of fins which where rotating at high velocity.  It was hovering above this hill for about 15 minutes if not more.  It disappeared instantly in a flash of lightning.
At that time in life, I was a conservative individual that had no awareness of the topic UFO’s.  I had not talked about it until later years in my life, when UFO’s where in the news.
By the way I would like to note that the date of the sighting may be wrong.  It was in June or July and in 1975 or 1976.
Sincerely,  ((name deleted))
Witness indicates that the date above is approximate.  PD