Well, there is this mod i’ve just tried this last week and i talked to one of the devs (Robcap) … They found sources for historical data/routes/early navigational data to recreate the first “guided navigation” route for airmail … anyways… find the details on the following post, and as PipsPriller is mentioned as the research guru in the thread, i think he might just be the guy you are looking for to hopefully find that data for/with you: