Which code is assigned to an aircraft as an identifier?

• A. Squawk code
• B. Flight number
• C. Registration number
• D. Flight plan code

Answer: (A)

The correct choice for the code assigned to an aircraft as an identifier is the squawk code. A squawk code is a unique, four-digit code assigned by air traffic control (ATC) to an aircraft for the purpose of radar identification. This code is entered into the aircraft's transponder and is critical for ATC to track the aircraft's position, altitude, and identify it on radar screens.

The squawk code serves as a specific identifier that distinguishes one aircraft from another, especially in busy airspace. It is typically assigned for specific flights during their operation and can change based on the airspace and flight phase. This dynamic nature is essential for real-time tracking and management of air traffic.

In contrast, other identifiers listed do not serve the same purpose as a squawk code. The flight number identifies a particular service for scheduling purposes but does not provide the radar tracking functionality of a squawk code. The registration number is a static identifier unique to each aircraft but is not used in real-time radar operations. Lastly, the flight plan code refers to the information filed with air traffic authorities prior to departure, which describes the planned routing and operational intentions but is not directly used for live identification on radar.