What must be done before issuing control instructions to an aircraft not in your airspace?

Before issuing control instructions to an aircraft that is not within your airspace, coordination with the appropriate controllers is essential. This process ensures that all relevant information is shared and that the aircraft is being handled in a way that complies with established protocols and air traffic regulations. By coordinating with other controllers, you can assure that any instructions issued are appropriate for the aircraft’s current position and flight plan, while also considering the airspace it will be transitioning into. This helps to maintain safety and efficiency in air traffic management, preventing potential conflicts or confusion between different air traffic control sectors.

While notifying nearby pilots and waiting for the aircraft to enter your airspace are important considerations in air traffic management, they do not adequately address the need for formal communication and coordination with the relevant controlling authority. Issuing instructions purely under your discretion without proper coordination could lead to dangerous situations.