Which flight condition leads to the greatest lift-to-drag ratio?

The greatest lift-to-drag ratio occurs at the best lift-to-drag angle of attack, often referred to as the "best L/D AOA." At this specific angle of attack, the aerodynamic forces producing lift and drag are optimized, resulting in the highest efficiency for the aircraft.

When an aircraft is operating at this angle, the lift generated is maximized relative to the drag experienced. Pilots and aerodynamics engineers use this information to determine the most efficient operating conditions for flight, especially during gliding or cruising phases when minimizing drag while maximizing lift is crucial for optimal performance.

In contrast, other flight conditions such as high speed with low angle of attack or low speed with high angle of attack do not achieve the optimal balance between lift and drag, which leads to a lower lift-to-drag ratio. Constant level flight might maintain altitude but does not inherently guarantee the best lift-to-drag performance compared to flying at the best L/D AOA. Therefore, the best L/D angle of attack is central to achieving the highest lift-to-drag ratio in aerodynamic design and performance.