What is the best endurance on a jet aircraft determined by?

The best endurance of a jet aircraft is primarily determined by the lift-to-drag ratio, specifically at its maximum (L/D max). This ratio measures the efficiency of the aircraft in generating lift relative to the drag it experiences. When an aircraft operates at its best L/D ratio, it can stay airborne longer on a given amount of fuel, thus maximizing its endurance.

A high lift-to-drag ratio means that the aircraft can produce sufficient lift while minimizing drag, allowing it to travel a longer distance per unit of fuel consumed. This is particularly crucial for maximizing endurance since the goal is to extend the flight duration without requiring additional fuel.

While factors like optimal cruising altitude, fuel capacity, and engine efficiency are important, they play a supportive role to the fundamental concept of lift-to-drag ratio in determining how efficiently an aircraft can fly, which ultimately impacts its endurance capabilities.