When should an advance descent clearance be issued?

An advance descent clearance is typically issued as appropriate and at a distance that allows the aircraft to achieve a normal descent profile and reduce speed effectively. This involves considering factors such as the aircraft's altitude, distance to the airport, current air traffic, and weather conditions. By providing this clearance in a timely manner, pilots can manage their descent more efficiently, leading to a smoother approach and landing.

Issuing the clearance based on situational awareness and optimal descent parameters helps maintain safety and efficiency in the airspace. It is crucial for air traffic controllers to use their discretion and knowledge of operational standards to determine the most suitable point to issue this clearance rather than relying solely on distance metrics or specific requests.