The great circle route from LA to London passes pretty close to Toronto.
"Don't they fly a great circle route? I don't think that would take them across the US."
"The great circle route from LA to London passes pretty close to Toronto."
The typical flight path from LA to London - LA to Vegas; head north from Vegas over Salt Lake; then over Idaho & Montana into Canada; over Hudsons Bay (as your chart shows); then over Greenland, sometimes far enough north to also fly over Iceland; southward from there over Scotland and on to London. The normal flight path over Canada is somewhat farther north than Toronto.
I have made this flight, LA to London or London to LA a couple dozen times, either in DC-10's or 747's. Even enjoyed a visit to the cockpit on a DC-10 once when we were over Greenland. I always enjoyed the trip.