Globe trotter
I made a version of this years ago as a way of learning D3's geography tools. Very few people knew how to play with geo-data before AI-led coding!
The map is Natural Earth's world at two scales: a coarse one for the whole globe and a finer one for short routes, both compressed into TopoJSON for performance. The route line is geodesic, meaning it's the shortest path between two points on a curved surface. If you move the globe a little, you'll see the line's curvature. Yes, I realise the travel times are optimistic! This assumes travel at a steady 900 km/h with no wind.
The airport data are from OurAirports. I built this with the d3-geo library.