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What does the transponder code 7700 indicate? That the aircraft is…

  • A

    Entering a controlled airspace without previous clearance.

  • B

    Experiencing a communication failure.

  • C

    Not receiving a radar service.

  • D
    In an emergency.

ICAO Doc 4444
8.5.2 SSR code management

8.5.2.1 Codes 7700, 7600 and 7500 shall be reserved internationally for use by pilots encountering a state of emergency, radiocommunication failure or unlawful interference, respectively.


Use the following mnemonics:
• Code 7500 = Unlawful interference ("75 - man with a knife")
• Code 7600 = Radio failure ("76 - I need a radio fix")
• Code 7700 = Emergency/distress ("77 - going to heaven")

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