What must pilots do post-resolution advisory after completing a collision avoidance maneuver?

After completing a collision avoidance maneuver, pilots are required to immediately notify the appropriate air traffic control (ATC) unit. This action is crucial because it ensures that ATC is aware of the aircraft's current situation and any necessary adjustments in traffic management can be made. Communication with ATC allows for the coordination of air traffic following the maneuver, thereby enhancing safety and situational awareness.

Notifying ATC helps maintain a clear understanding of the airspace situation, as controllers need to monitor the movements of all aircraft to prevent further conflicts. This immediate communication is part of the standard operating procedures intended to promote safety and efficiency in the airspace system.

In contrast, returning to the assigned flight level, changing the destination, or canceling the flight plan are not standard requirements following a resolution advisory. These options may be appropriate in different circumstances but do not directly pertain to the post-resolution advisory protocol that emphasizes communication with ATC.