What is a “Squawk”?

Squawks, or squawking, has its origins in The Second World War, where IFF systems were first installed. These Identification Friend or Foe systems were established in response to control friendly fire by establishing a two-way transponder system. One where air traffic control (ATC) effectively request an aviation vehicle to identify themselves as either a “friend” or remain silent, where ATC can assume – not confirm – a “foe.” This IFF system was codenamed parrot during the war and hence the modern term “squawk.”

Since World War II, squawking has evolved somewhat, and today a squawk refers to a discrete transponder code. These codes are four digit numbers that each respond to secondary surveillance radar interrogation signals sent by ATC to uniquely identify an aircraft on a radar.

Squawk Transponder Codes and their meanings

Squawk codes are formed of four digits that read from 0 to 7; the highest code available is 7777 and the lowest is 0000. Between them, squawks can be one of 4096 transponder code combinations, where each code is assigned to a different meaning that is then used to correlate the reply with the squawking aircraft’s flight plan.

These codes can be used in emergencies, where there is no flight plan correlation needed and in more specific circumstances. For instance, 7500, which is an emergency code signalling to ATC that the aircraft has been hijacked, 7700 signals a more general emergency and 7004 refers to the code used for aerobatic and display planes in the UK. To see a full list of transponder code assignments, click here.

Why is Squawking Important for Flight Tracking?

Squawks are not only central to ATC’s flight tracking capabilities, but they also are instrumental in ensuring a continuous flow of communication between pilots and controllers. It is this openness that ensures all airspaces remains safe and efficient.

Squawking is important for flight tracking, especially from the perspective of those on the ground, as these specific transponder codes not only allow a safe form of communication between ATC and pilots but allows in-depth flight tracking. Not just location, speed, altitude and aircraft type, but it allows flight tracking to become situational.

This is especially the case in emergency situations because too often, in these high-pressure scenarios, pilots rarely have the time to ensure said emergency is communicated properly. However, transponder squawk codes allow ATC on the ground a level of insight into your situation which, in turn, allows them to ensure the correct aid is ready and waiting at the nearest airport if required.

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