17. (1985) Per schedules available in the 1985 North American OAG I used to reference these questions, only two airlines still offered service to Toronto’s Lester Pearson International Airport with McDonnell-Douglas DC-8s – one with a standard DC-8 and the other with a stretch DC-8. Identify each airline, the DC-8 variant it served YYZ with and where each flight came into Toronto from.
I have to believe that the -50 was Aeromexico, probably a less-than-daily service from Acapulco/ACA; both Air Canada and CP Air had retired their Stretch 8s a couple years ago, as had Air Jamaica, so maybe this example at YYZ was a United turn from Chicago/ORD
AeroMexico is indeed one of the airlines. United would seem a very likely choice and yet - we're looking for a different DC-8 operator. Please, carry on!
The other candidate would probably be Nationair with the stretch. Guessing it came from YMX (tag on from Europe).