of course there were fewer flights and fewer airlines in the days of pen and paper..............

The printed OAG books certainly survived well into the 1990s.

In another life I spent many hours poring over them, attempting to reverse-engineer route networks of potential airline clients with varying degrees of success.

The way that I now reverse engineer is a route is:

• Wikipedia
• Select country/city
• Select transport / Air
• Very lovely people have listed the carriers and destinations.
• Find one that will probably match your usual carriers
• Check routes from your usual airport/s

The ABC was invaluable in its day and a good library would subscribe. (I have a shelf full of obsolete editions bought at £1 or £2 per issue.) The problem is that codeshares and flights operating on odd days made it ever more difficult to read and it only went a month or so ahead.

Online timetables timetables can be a pain because you have to input a date. Sometimes you want to know if a flight operates throughout a timetable period and that can be difficult to find. You have to know which airlines operate a route which requires a level of knowledge (and knowing about alliances can help). Not every flight is daily which can cause problems. Some airlines such as QF give the choice of a daily and weekly timetable which is helpful depending on whether you want to fly from SYD - MEL or long haul to a station with an infrequent service. Others might like to.

I did round the world trips in 1990 & 1995. If I was doing the same today I might struggle. I have access to the OAG Cargo Guide which gives widebody passenger flights, websites like FR24 & internet message boards. But where does someone who is not interested in aviation start?

They start with Google Flights and Wikipedia
I think the big 3 alliances have specialised websites to help plan RTW trips

"Online timetables timetables can be a pain because you have to input a date. "

Especially annoying if it's not a daily flight! You have to keep putting in dates until you find one

the best sites will suggest an alternative if the date you have has no flight or its fully booked - but most are rubbish

I have certainly noticed - before Covid - that online timetables are very sketchy. They do not want to commit to showing dates too far ahead when they might reduce the service. The electronic era allows them a freedom their forbears could only have dreamed of.

Update
I have just tried to find some Air New Zealand flights and they have a daily timetable but not a weekly timetable. Yet many of their long haul flights are less than daily. I typed 'Weekly timetable' into the help box & got the reply that they no longer produce a weekly timetable and to use the booking function. The information is there but boy its clunky to use. I had to go through an I'm not a robot test & then click on each day for the times. You can use FR24 to look at current flights but not into the future and schedules will be seasonal. Why do some airlines make everything so difficult!