The customer is always right

The shortest distance between two points is always a straight line in conventional geometry. 

 This is geometry usually learned in school, where shapes are two-dimensional and represented on a flat surface like a notebook paper. In real life, the shortest distance is a curve called a geodesic. This is because our planet is not flat! Thus, not traditional geometry, but Riemannian geometry, is used. This is the concept that flight planners use to plot aircraft trajectories in order to save time and fuel. From a practical point of view, in most cases, geodesy is the shortest curve connecting two points. This effect has interesting implications; For example, when you're flying on an airplane, the path you take to get from one destination to another does not follow a "straight line", as many people imagine. It follows the "curvature" of the ground, while making small adjustments in the direction of movement, in order to cover the shortest possible stretch. If the plane is simply "in a straight line", it will end up traveling a longer path than when following the curvature of the Earth #Transported