99C.
So the airline is probably middle-east or South Asia (but not east Asia). Make the 1st stop IAD if it's UA.for the 2nd flight to PDX. so XXX--(ZZZ?)-YYZ-IAD. Of those only 3-5 have ever flown to Canada in the past other than in the past decade or so and ~2-3 to YYZ and looks like only 2 operated 747-200Cs in the time frame.. Pakistan?