How many airport charts do airline pilots have in the cockpit?
In the 1990s I flew for two 747 carriers, the first primarily a freight carrier and the second primarily a passenger carrier. Both used Jeppesen for their airway manuals, and both supplied each pilot with a single, full-size and very full Jepp manual that contained as many as possible of the airports we might go into. Image below:



As I remember, the criteria for whether a plate would be in our personal binder included the airport having a runway at least 5000 feet long.

Both carriers did extensive charter work to every continent save Antarctica, and we would occasionally be dispatched to an airport that our personal Jepp manual didn't have. The freight carrier handled this problem by having aboard each aircraft a flight bag with full, world-wide coverage, 5 or 6 manuals as I remember. In theory the manuals were kept current by updating them each time the aircraft went through its base, but in practice they were almost always out of date, but at least they were there in case of an inflight diversion to an unplanned airport.

The pax carrier handled the problem of an airport not in our personal coverage by faxing the plates with our flight plans. In case of an unplanned inflight diversion, dispatch would read the pertinent information to us over HF, a very tedious procedure, obviously. I only had that happen once.

It was a different world back then with no ubiquitous Internet. I typically spent 300 to 400 dollars per month in international phone calls to my wife. No Skype, no WhatsApp, Compuserve for email until around 1996 or so, then sporadic Internet, but always dial-up and with ridiculous charges by the hotels.