Flight routes and map projections - Datawrapper Blog
Airline Route Maps
Open-source airline route maps from 1999 and 2018 created using Python and BTS data (see corresponding comment for clarifications + GitHub link) [OC] : r/dataisbeautiful
T.W.A. Air Routes.: Geographicus Rare Antique Maps
The Design History of Airline Flight Maps - Bloomberg
FlightConnections - All flights worldwide on a map!
Route Maps – Northwest – Northwest Airlines History Center