I think it's the one that used to be Aeronaves de Mexico. Rode their DC-6s a couple of times Mexico City-Acapulco in 1960-61. I remember especially the captain out on the wing with a dipstick measuring the fuel load.
.The Acapulco airport in those days was not much more than a shack. Once there was a well dressed, obviously rich fortyish Yanqui lady passenger with her twentyish boyfriend waiting across the room from us, while a large rat capered around next to her feet. Somehow reminded me of "Night of the Iguana" or some other Liz Taylor movie. Happy bygone days!
At least that's what the Mackey captain was always doing . . . .