For an aircraft to remain in FLAT Track during adjustments in route, what must a controller do?

For an aircraft to maintain a FLAT Track during route adjustments, it is essential for the controller to enter the amended route into the system. This action ensures that the aircraft's flight path is updated to reflect any changes made to its intended route. By entering the amended route, the controller provides necessary navigation information that aligns with the aircraft’s current position and flight plan.

Maintaining a FLAT Track relies on precise data management within the radar system to ensure that all flight information is synchronized and that the aircraft is following the correct path. This is crucial for maintaining safety and efficiency in air traffic management, as it helps avoid conflicts with other aircraft and optimizes routing.

While contacting the pilot can be part of communication protocols, it does not directly affect the tracking of the aircraft's route in the radar system. Similarly, changing the altitude or monitoring the aircraft's speed are related aspects of air traffic control but are not specifically what keeps the FLAT Track operational following a route adjustment. Entering the amended route directly addresses the necessary changes for the radar system to reflect the aircraft's new course.