Just some notes on OAG etc.
OAG was long seen as a US product, it was an offshoot from the long-established railway equivalent ORG, whose older editions also usefully contain airline schedules (a bit condensed). I like the way the older ones I have (eg 1960) are just straight prints from a computer line printer of the time, with wobbly character justification. I could never get my head around their approach of collating the schedules by destination rather than origin however, the reverse of normal practice. They long had two volumes, North America and Rest of the World, and I get the impression that most of what is now available in the USA is the domestic one, which must have had a much greater circulation.
From the UK, and indeed across much of the rest of the world, the equivalent was the ABC, which also grew out of a railway timetable publisher. First edition was 1946, and I have one - don't think I've got something of great value, though, because the publisher did a reprint run of it in 1996 for the 50th anniversary, and it's actually pretty thin on content anyway. When it got too big for one volume in the 1960s they moved on to two volumes as well, but splitting the alphabet instead so you always need both. ABC eventually bought out OAG, but the continuing product was named OAG although it is to the old ABC format.
There was a third publication, also from the UK, which was Bradshaw's Air Guide, yet another outgrowth from a railway timetable publisher, which became popular pre-WW2 and continued until 1956 when it was closed down. I have several of these from the 1940s/50s, they are a much more convenient size than ABC, and were always fully in "timetable" format rather than quick reference, with some very clever manual editing and typesetting to minimise paper taken and yet get everything in (their UK-wide train timetable was the same). How Bradsahw and ABC managed to gather worldwide data in the 1940s/50s (and they appear remarkably complete) has to be a great achievement.