What should a controller do upon determining that an aircraft is out of lateral tolerance?

When an aircraft is determined to be out of lateral tolerance, the appropriate action is to switch it to free track status. This step allows the radar controller to monitor the aircraft without further automated lateral guidance from the radar system, essentially enabling the controller to maintain visual radar contact while the pilot handles any necessary navigation maneuvers.

This approach is significant because it provides the controller with greater flexibility in assessing the aircraft's position and maintaining safe separation with other traffic. Free track status removes the imposed lateral constraints that may contribute to complications in navigation, allowing for a more hands-on, coordinated approach to addressing the situation as it develops.

The other options, while they relate to different controller actions, do not directly address the issue of lateral tolerance. For instance, changing the radar code might serve to refresh or transfer data but would not necessarily assist in correcting the lateral deviation. Notifying the pilot immediately might be essential, but it is generally performed in conjunction with adjusting the aircraft's status and managing the situation. Contacting air traffic management could be warranted but is typically a step taken after immediate remedial actions like changing the status of the tracking.