What is the most direct route over the earth's surface that saves time and money for pilots?

The most direct route over the earth's surface that effectively saves time and money for pilots is the great circle route. This route represents the shortest distance between two points on the surface of a sphere, taking the curvature of the Earth into account. Consequently, when aircraft navigate using a great circle route, they optimize fuel consumption and reduce flight time.

In contrast, a rhumb line, while simpler to navigate since it maintains a constant compass bearing, results in longer distances, especially over longer flights, which can lead to increased fuel costs and travel time. Airway routes are also predetermined paths that may not always represent the most efficient routes based on the great circle principle, as they have to accommodate existing air traffic systems and safety requirements. The term "flight path" refers to the specific route that an aircraft follows during its flight, which can vary based on air traffic control instructions, weather conditions, and other factors, rather than being inherently the most efficient.