Great Circle

Great Circle is the shortest path between two points on the surface of a sphere (Earth). Great circle routes are the basis for efficient long-distance flight planning, as they minimize distance and fuel consumption compared to straight lines on a Mercator projection (rhumb lines).

Great circle routes between mid-latitude points often curve significantly toward the poles. For example, the great circle route from New York to Tokyo passes near Alaska. Flight planning systems compute great circle distances and then adjust for winds, airspace restrictions, and ETOPS constraints.