Has anyone found a site that gives airport-to-airport distances directly on the GRS80/WGS84 spheroid-- i.e. without having to look up the lat-lons?
uses the Clarke 1866 spheroid, so its mileages are better than many, but they can still be off by a few miles.
apparently uses a spherical earth, as do most other sites.
If you find a possible site and want to test it, try HNL-RAR, which should come out 2542.3 nm, and LED-ANC, which should come out 3556.8 nm. Also, the equator to the 45th parallel should be 2691.655 nm, while 45 degrees to the pole is 2708.975.