Which piece of information is NOT required when forwarding data for military or scheduled air carriers?

The requirement for forwarding data for military or scheduled air carriers primarily focuses on facilitating safe and efficient aircraft operations. Each of the listed pieces of information serves a specific purpose in maintaining operational integrity and communication.

ETA at destination is crucial for overall flight management and ensuring that air traffic control can manage airspace effectively. It helps in predicting traffic flow and necessary adjustments during the flight, but it is not strictly required in the same way the other pieces of information are.

Aircraft ID is fundamental for identifying the specific aircraft in communication. This information is essential for air traffic control to track and manage the aircraft during its flight.

Altitude assignment is critical as it ensures separation between aircraft flying at various heights. This information is vital to maintain safety and prevent mid-air collisions.

Remaining route of flight provides air traffic controllers with necessary routing information and is essential for ensuring that the aircraft follows planned airways and avoids restricted or hazardous areas.

Thus, while ETA is important, it is not as critical as the other pieces of information, making it the appropriate choice for the piece of information that is not required.