Which IFF mode is commonly used for air traffic control?

Which IFF mode is commonly used for air traffic control?

• A. Mode 3A.
• B. Mode 1.
• C. Mode 4.
• D. Mode X.

Answer: (A)

Mode 3A is what air traffic control relies on. In this mode, the aircraft’s transponder replies with a four‑digit octal code—the squawk—assigned by ATC. Controllers use that code to uniquely identify and track each aircraft on radar, mapping the aircraft’s position to its identity and maintaining safe separation. This simple, widely supported identification method is the standard for civil aviation and ATC operations. Other modes serve different purposes: Mode 1 is a military-specific mission code, not used for civilian ATC identification. Mode 4 provides cryptographic authentication for secure military identification, not for routine air traffic control. Mode X is not the standard for civilian ATC and is not used for typical ATC identification today.

Mode 3A is what air traffic control relies on. In this mode, the aircraft’s transponder replies with a four‑digit octal code—the squawk—assigned by ATC. Controllers use that code to uniquely identify and track each aircraft on radar, mapping the aircraft’s position to its identity and maintaining safe separation. This simple, widely supported identification method is the standard for civil aviation and ATC operations.

Other modes serve different purposes: Mode 1 is a military-specific mission code, not used for civilian ATC identification. Mode 4 provides cryptographic authentication for secure military identification, not for routine air traffic control. Mode X is not the standard for civilian ATC and is not used for typical ATC identification today.