What is an authorization by ATC for the separation of aircraft called?

The term that refers to an authorization by Air Traffic Control (ATC) for the separation of aircraft is known as ATC clearance. This authorization is essential for ensuring the safe and efficient management of air traffic, allowing controllers to provide pilots with specific instructions regarding takeoff, landing, and in-flight maneuvers.

An ATC clearance includes instructions that can pertain to altitude, departure procedures, and specific routes to follow, all designed to maintain safe distances between aircraft and minimize the risks of collisions. This process is critical in crowded airspaces, where multiple aircraft may be operating in close proximity. The use of clearance systems enables pilots to have a structured understanding of their movements and obligations as they navigate through airspace.