A great circle route is used to save time and fuel by flying the shortest distance between two points on the surface of the Earth. This route follows the curve of the Earth's surface, which is a sphere, and is the shortest distance between any two points on it. Using a great circle route, airplanes can avoid flying over long distances, such as deserts or oceans, and also avoid flying near the north pole. By taking the shortest distance possible, airlines can save both time and fuel, making their flights more efficient and cost-effective.