When transferring control responsibility between facilities, at what point should the transfer be made?

The transfer of control responsibility between facilities should be made at a designated time fix or altitude because this ensures a clear, organized, and safe transition of air traffic control responsibilities. This practice aligns with standard operating procedures that are designed to maintain safety and reduce the risk of communication errors or mismanagement of aircraft during critical phases of flight.

By transferring control at a specific fix or altitude, controllers can ensure that both facilities are on the same page regarding the aircraft's position, heading, and intention. This minimizes confusion that could arise from an immediate transfer based solely on pilot requests or after deviations, which may happen unexpectedly. Specifying a designated time or location means that both the outgoing and incoming controllers have adequate situational awareness and are prepared to manage the flight effectively, allowing for continuous air traffic management and safety.