Squawk 7700: The Four-Digit Codes That Speak for a Silent Cockpit

Every aircraft flying in controlled airspace carries a transponder, a small radio that answers interrogations from ground radar and reports the aircraft's identity and altitude. Controllers assign each flight a unique four-digit code — the "squawk" — so a single blip on a crowded screen becomes a labeled, tracked flight with its altitude displayed alongside. Mode C adds automatic altitude reporting; the newer Mode S and ADS-B extend the system with richer data and satellite-based precision. Three codes are reserved worldwide as universal distress signals, and they are taught to every pilot as a kind of emergency vocabulary. Squawk 7700 declares a general emergency: dialed in, it lights up the aircraft on every controller's scope in range, instantly flagging that this flight needs priority and help. Squawk 7600 signals lost communications — the radio has failed, and the pilot is telling the system "I can hear nothing; I will follow the expected procedures." Squawk 7500 is the gravest: unlawful interference, the discreet signal for a hijacking. The elegance of the system is that it works when words cannot. A pilot overwhelmed by an in-flight emergency, or one whose radios have died, can communicate the essence of the situation with a few turns of a knob, and the entire ground apparatus reorients to assist. Controllers will clear airspace, roll emergency equipment, and provide whatever help the situation allows. The codes and procedures are codified in the FAA's Aeronautical Information Manual. They are a quiet piece of design genius — a shared, wordless language for the moments when a cockpit most needs to be heard. The decision to declare an emergency, and the authority to deviate from any rule to meet it, belongs to the pilot in command under 14 CFR §91.3.