What is the minimum required spacing between aircraft flying above FL 600 for safety?

The minimum required spacing between aircraft flying above FL 600 is established to ensure safety and prevent potential mid-air collisions. In high-altitude air traffic management, maintaining adequate separation is critical due to the high speeds at which aircraft operate and the reduced ability of pilots to take evasive action at such altitudes.

The correct answer, which specifies a separation of 10 nautical miles, aligns with the regulations set forth by aviation authorities. This distance is based on operational data and safety assessments that have deemed it sufficient to allow for the mitigation of risk in scenarios where aircraft may be converging or transiting in close proximity.

In contrast, the other options reflect distances that either do not meet safety standards or are below the recommended thresholds for high-altitude operations. Therefore, adhering to the 10 nautical mile spacing is essential for maintaining a safe en-route environment for aircraft operating above FL 600.