Earth Distance Calculator
You can check how accurate it is here:
This project finds how far, on Earth, two places are given their latitude and longitude. Its not the simple 3D Pythagoras, but rather, a formula called the Spherical Law of Cosines. Also it is based on the Haversine formula. Thanks to @DadOfMrLog for telling me how to do this.
Latitude 90 = North Pole
Latitude -90 = South Pole
Latitude is up and down, Longitude is around the equator.
Keywords: earth distance flying calculator haversine formula trigonometry math maths geo geography planet sphere spherical latitude longitude curve