Well if you haven't heard of this airline, the odds're pretty good I haven't either. Short of going online and looking it up in a Mexicana timetable, how 'bout a hint? Say... the first seven letters in its name or perhaps an aircraft type? When I spent four months in Oaxaca back in 1975, there was a Quintana Roo based airline that used to run a DC-3 from OAX down to Puerto Escondido. Another outfit went up to Merida. Aerolineas Maya or some such. Regardless, I can't with certainty recall any Mexican airlines from that region that operated in the 60s.

En el peor de los casos, siempre podemos esperar que quizás WHBM se apiade de nosotros y nos de la respuesta correcta!