When and how are greyed out entries in the ACL removed?

The removal of greyed out entries in the Access Control List (ACL) occurs when aircraft are no longer on frequency. This process ensures that the list remains current and relevant by eliminating entries that pertain to aircraft no longer in communication with the radar system. When an aircraft is actively communicating, it remains visible in the ACL for the safety and efficiency of operations. Once the aircraft ceases communication—indicating it has departed the airspace or is no longer operational—its entry is greyed out and eventually removed.

This process is crucial for maintaining a clean and manageable radar environment, allowing air traffic controllers to focus on active and relevant entities. It helps eliminate confusion over aircraft that are no longer a factor in airspace management, streamlining communication and tracking.

Other options may not accurately reflect the procedure regarding the management of greyed out entries. For instance, while the landing of aircraft could result in them being no longer on frequency, it is not a direct cause for their removal from the ACL, as the key factor is their communication status. The end of a shift or automatic system actions do not specifically relate to immediate removals but rather to broader operational protocols that may influence overall documentation and tracking systems.