What is the minimum horizontal separation required for aircraft above Flight Level 600?

The minimum horizontal separation required for aircraft operating above Flight Level 600 is 10 miles. This standard is established to ensure the safety and efficiency of air traffic operations at high altitudes where aircraft encounter a variety of factors, such as increased speeds, reduced ability to maneuver due to altitude, and the potential for more complex flight paths. At these higher altitudes, the risk of wake turbulence and other hazards increases, necessitating a greater distance between aircraft to prevent potential conflicts.

Other options do not align with the established guidelines for separation at these altitudes. The required distance is designed to provide a balance between safety and airspace efficiency, and 10 miles allows sufficient buffer while still maintaining effectiveness in air traffic management.