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
Create a flight map of your travels - The Airline Blog
How To Make Flight Maps - One Mile at a Time
Direct Flights - International Flight Directory - Made with React.js
AirTreks TripPlanner: Plan Your Multi Stop Trip Today