What determines whether an aircraft remains in FLAT Track during navigation changes?

The condition for an aircraft to remain in FLAT Track during navigation changes is directly related to the entry of an amended route. When a route is amended, it provides updated information regarding the aircraft's intended flight path, which is crucial for maintaining effective air traffic control. This is particularly important as any changes in the route must be communicated so that the radar system can accurately reflect those changes, allowing for efficient separation and management of air traffic.

The necessity for an amended route suggests that radar controllers need to have real-time, updated data on an aircraft’s progress and trajectory. If an aircraft needs to divert or alters its course due to weather, airspace restrictions, or other operational considerations, the controller will enter this information into the system to ensure that the aircraft can remain on FLAT Track smoothly. This allows for a continuation of the aircraft's progression towards its destination without unnecessary conflicts or deviations from the planned path. The accuracy of this data entry is critical to maintaining safe and efficient operations in controlled airspace.