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Aviation glossary

Squawk code

Also: squawk, transponder code, SSR code, Mode A code

Operations and flight

A four-digit number, each digit from 0 to 7, that air traffic control assigns to a flight and the transponder transmits to identify it on radar screens.

What it is

Each digit runs from 0 to 7 because the system is octal, giving 4,096 possible combinations. ATC assigns a code to each flight, often with the departure clearance, and the radar system automatically links it to the flight's call sign and flight plan.

ICAO reserves certain codes for special situations: 7700 signals an emergency, 7600 a radio communication failure and 7500 unlawful interference. In Europe, 7000 is the usual code for visual flights without an assigned code; in the United States the equivalent is 1200.

With Mode S and its unique 24-bit address, the code has lost some of its role, but it remains the way controllers and crews confirm a flight's identity. When ATC asks a pilot to ‘squawk ident’, a press of a button makes the aircraft stand out on the controller's screen for a few seconds.

Related terms

TransponderAn on-board device that answers secondary radar interrogations with an identity code, its altitude and, in Mode S, a unique 24-bit address. Air traffic controlThe service that keeps aircraft safely apart and orders traffic on the ground and in the air through clearances and instructions passed by radio. Mayday and pan-panStandard radio calls for declaring an emergency: ‘mayday’ signals grave or imminent danger, ‘pan-pan’ an urgent situation that needs no immediate help. ADS-BA system in which an aircraft automatically and regularly broadcasts its satellite-derived position, altitude, speed and identity by radio. Call signName by which an aircraft is identified in radio communications with air traffic control, such as Speedbird or Lufthansa followed by the flight number.
Whole glossary

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This page was last updated on October 9, 2026

APA

Vuelopedia. (2026, October 9). Squawk code. Retrieved October 16, 2026, from https://vuelopedia.org/en/glossary/squawk-code

MLA

“Squawk code.” Vuelopedia, Fundación Poderia, 9 Oct. 2026, vuelopedia.org/en/glossary/squawk-code. Accessed 16 Oct. 2026.

Chicago

Vuelopedia. “Squawk code.” Fundación Poderia. Last modified October 9, 2026. https://vuelopedia.org/en/glossary/squawk-code.

Harvard

Vuelopedia (2026) Squawk code. Available at: https://vuelopedia.org/en/glossary/squawk-code (Accessed: 16 October 2026).

BibTeX

@misc{vuelopedia_en_glossary_squawk_code,
  author       = {{Vuelopedia}},
  title        = {{Squawk code}},
  publisher    = {Fundación Poderia},
  year         = {2026},
  date         = {2026-10-09},
  url          = {https://vuelopedia.org/en/glossary/squawk-code},
  howpublished = {\url{https://vuelopedia.org/en/glossary/squawk-code}},
  urldate      = {2026-10-16},
  note         = {Accessed 2026-10-16}
}

Wikipedia

{{cite web |url=https://vuelopedia.org/en/glossary/squawk-code |title=Squawk code |website=Vuelopedia |publisher=Fundación Poderia |date=2026-10-09 |access-date=2026-10-16 |language=en}}

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