What should be stated when an aircraft is leaving an assigned altitude after a descent clearance?

When an aircraft is leaving an assigned altitude after a descent clearance, the phrase "Report leaving assigned altitude" is used to ensure that pilots communicate their altitude change clearly with air traffic control. This is essential for maintaining situational awareness, both for the controller and for the pilot. By reporting when they leave the assigned altitude, pilots provide the controller with immediate data about their vertical position, which helps in maintaining safe separation from other aircraft.

This specific phrase confirms the action taking place, which can be particularly important in busy airspace where multiple aircraft may be changing altitudes simultaneously. It also prompts the pilot to accurately monitor altitude changes as they transition through various levels, as safety protocols often require awareness beyond just the descent itself. Such communication enhances the overall safety and efficiency of air traffic management.