Which mode of IFF operation is used by military and civilian aircraft control stations?

Mode 3/A is the correct choice for the mode of IFF (Identification Friend or Foe) operation used by both military and civilian aircraft control stations. This mode provides a means for air traffic control and military systems to identify and differentiate between friendly and potentially hostile aircraft in airspace.

Mode 3/A operates in a way that allows transponders in aircraft to respond to interrogations from ground control antennas with a unique coded signal. This enables air traffic controllers to monitor and manage air traffic effectively, ensuring safe separation and identification of aircraft operating in shared airspace, which includes both civilian and military operations.

The significance of Mode 3/A lies in its widespread adoption; it is a standardized modality that has been implemented globally, which facilitates cooperation between military and civilian aviation operations. This shared use is vital for maintaining situational awareness and safety in aviation, particularly in regions where both military and commercial flights are active.