Definition
A flight path that follows the shortest distance between two points on the surface of the Earth, measured along the curve of a circle whose center is the center of the Earth. Because the Earth is a sphere, this shortest path is curved rather than straight when drawn on a flat map, and the true course along it changes continuously as the aircraft moves.
Plain English
The shortest possible route between two points on the globe. Because the Earth is round, this route curves on a flat map and the compass heading slowly changes as you fly along it.
Context Anchor
Seen when filing or reading random area navigation (RNAV) routes, where route segments between navigation points may be based on Great Circle tracks.
Derivation
A 'great circle' is any circle drawn on a sphere whose center matches the center of the sphere itself, making it the largest possible circle that can fit on that surface. The equator is one example. Any slice through the Earth that passes through its center traces a great circle, and the shortest path between any two points on Earth always lies along one of these circles.
Why Pilots Care
It is the shortest and most fuel-efficient route between distant points, especially useful for oceanic or polar operations.
Analogy
Stretch a string tight between two cities on a globe. The path the string takes is the Great Circle track. On a flat wall map that same path looks like a curve, not a straight line.
Grounding Statement
On a globe, the shortest path between two far-apart points is often not the same shape you would draw by eye on a flat chart.
Intuition Check
A Great Circle track is not a circular route. It means the shortest path over the Earth’s surface between two points, and it may require changing direction along the way.
Example Sentence 1
The flight planning system computed a Great Circle track from the departure fix to the oceanic entry point, shortening the route by nearly forty miles.
Example Sentence 2
When planning the polar flight, dispatch chose the great circle track to minimize total distance and fuel burn.