"I traversed down the state tree until I found the allAirportsList property, which contained all the airport keys and the locations to which they flew. I extracted this state (over 1MB of route information) and could now build a graph representation of airport connections."
In the 90's, I can remember a pocket-sized, printed guide by a company called OAG. I used to call it "the OAG Guide". I can remember getting a copy of this for free. It listed every schedule for every route for every airline. I can also remember getting similar pocket-sized guides from certain airlines listing all their routes and schedules for each route.
When the task of planning routes comes up, I sometimes think of those old printed guides and wonder if this could be cited as an example where certain information was actually more easily accessible before the www became popular than after.