When is an aircraft permitted to resume its own navigation?

An aircraft is permitted to resume its own navigation when it is within radar coverage and has received specific permission from Air Traffic Control (ATC). This protocol ensures that ATC maintains situational awareness and is able to provide necessary separation between aircraft. Being within radar coverage allows ATC to track the aircraft's position and movements, which is crucial for maintaining safety in controlled airspace. By permitting pilots to navigate independently under these conditions, ATC can effectively manage traffic and allow for more efficient routing while still ensuring safety protocols are adhered to.

The other options suggest circumstances that do not align with standard navigation procedures. Resuming navigation only during emergencies, or requiring a pilot report to ATC without considering radar coverage, could lead to safety issues if not properly managed. Additionally, descending below minimum altitudes is not a condition for regaining navigation responsibility but rather a critical action that must adhere to strict altitude requirements for safety.