Huge, black triangle with many orange lights in 2 rows passed slow and low, silently with no exhaust 1989

My Mother and I had just reclined on our lawn chairs to watch the twilight and enjoy the lingering warmth of a windless evening.  We were looking at the sky, looking south.  A huge, black triangle appeared before us just over the roof of the neighbour south of us.
We both saw it, both screeching, "What is that?"  It was so low and so big.  We could see orange light bulbs in lines down the two sides.  It was completely silent and had NO exhaust.  Had there been exhaust, I would have been able to see it.  
I thought immediately that it was atomic powered.  It was not gliding. It passed slowly, with an even speed, and in a straight line.  The little orange lights looked vaguely comical.
I got up and ran out to the front of the house to follow it but it went over the neighbour`s house and quickly was out of sight.  There was no way to follow it as it passed on an angle to the streets.  
I called the UFO hotline in Toronto.