The History of SQUAWK
You might think that the term SQUAWK comes from the sounds that birds use to communicate. And, in reality, the term referring to communication from something flying through the sky does originate from a bird. But the history of the term SQUAWK is a bit more complex.
SQUAWKing was a term that was made up during World War II, when "Identification Friend or Foe" (IFF) systems were set up on airplanes so that it was possible to determine whether an aircraft was an ally or an enemy, and avoid any friendly fire. To let air traffic control know that a plane was "friendly," a two-way communication system was set up using a transponder. Air traffic control would put out a request for an aircraft to identify itself. If the aircraft identified itself with a code, then they established themselves as friendly. The IFF system was codenamed "Parrot" during the war, and it took on the term "SQUAWK" to determine the actual process of communicating.
Today, SQUAWKing doesn't just refer to instances in which air traffic control directly contacts an aircraft. Instead, SQUAWKing refers to a specific transponder code that aircraft can use to identify themselves or send a specific message to air traffic control. SQUAWK codes are four digits and they are used to easily identify a specific aircraft when detected on a radar, or to determine what an aircraft needs in the case of an emergency or situation in which a flight plan needs to be changed.
