The whole point of Great-circle routes is that they are (effectively) straight lines. They just appear not to be on 2d projections of an oblate sphereoid — you

The whole point of Great-circle routes is that they are (effectively) straight lines. They just appear not to be on 2d projections of an oblate sphereoid — you know, a "map" of a "planet". From Wikipedia, "The minor arc of a great circle between two points is the shortest surface-path between them. In this sense the minor arc is analogous to “straight lines” in spherical geometry." [1] [1] https://en.wikipedia.org/wiki/Great_Circle https://en.wikipedia.org/wiki/Great_Circle