Great Circle Route

The shortest distance between two points on the surface of a sphere, formed by the intersection of the sphere with a plane passing through both points and the center of the Earth. On a standard Mercator-projection chart, a great circle route appears as a curved line, while on a Lambert conformal conic chart (used for sectional charts), it approximates a straight line. For long cross-country flights, flying the great circle route saves fuel and time compared to a constant-heading rhumb line, though the heading must be continuously adjusted along the way.