To obtain maximum distance over the ground, the airspeed to use is which of the following?

• A. Best L/D (lift/drag) speed
• B. Maximum speed
• C. Stall speed
• D. Cruise speed

Answer: (A)

To maximize distance over the ground, you want the speed that gives the best lift-to-drag ratio. This is the best L/D speed, the point where the glider converts altitude into forward travel most efficiently. At this speed the glide ratio—the horizontal distance you can cover per unit of altitude lost—is at its highest, so you can glide farther from a given height.

In practice, flying faster usually increases drag faster than lift, reducing the glide ratio and the distance you can cover before landing. Stall speed is the minimum speed to maintain flight and would yield little forward motion, while maximum or cruise speeds prioritize speed over efficiency and don’t maximize ground distance. Wind can change actual distance, but the underlying principle remains: best L/D speed gives the greatest distance for a given altitude.