What should be entered to remain in FLAT track?

To remain in FLAT track, entering the amended route is essential. The purpose of a FLAT track is to ensure that an aircraft continues on a pre-defined route while allowing for adjustments as necessary. When conditions change—such as air traffic, weather, or operational requirements—the route may need to be amended to ensure safe and efficient flight operations. By entering the amended route, controllers can provide updated guidance that reflects these changes, keeping the aircraft on a designated path and ensuring that it adheres to air traffic management protocols.

Entering the original flight plan alone does not account for any necessary adjustments that may have arisen after the flight's departure. A new altitude may be relevant for certain flight operations and airspace considerations but does not specifically address the route of flight. Similarly, a new beacon code is primarily used for identification and tracking purposes rather than indicating a need to adjust the route itself. Therefore, amending the route keeps the aircraft in compliance with current operational conditions while in FLAT track.