Which IFF modes are shared by both military and civilian air traffic control?

In the context of Identification Friend or Foe (IFF) systems, modes 3/A and C are indeed shared by both military and civilian air traffic control. Mode 3/A is commonly used by civilian aircraft for air traffic control, providing a simple transponder response that identifies the aircraft. This mode helps controllers in monitoring and managing air traffic effectively.

Mode C is an enhancement that includes altitude information, which is crucial for air traffic management as it allows for vertical separation of aircraft, facilitating safer operations in crowded airspace. This altitude reporting is essential for both military and civilian operations, ensuring that all air traffic is adequately tracked and managed.

In contrast, the other modes listed are not universally used or applicable across both military and civilian domains. This specificity in the functionality of modes 3/A and C supports their shared usage, making them a critical part of the air traffic control system for both sectors.