When an air traffic controller starts their shift, they begin an often unceasing task of managing airplanes that are landing, taking off, or traveling through their airspace, using squawk codes. In a busy area, this can mean constant, careful coordination, and nonstop communication to various aircraft. Yet almost unbelievably, very rarely is an aviation incident due to a fault of air traffic control (ATC).
So how are all these airplanes successfully managed from a tower that can’t even see the pilots they’re talking to? Part of the answer is the amount of experience necessary to do the job of an air traffic controller. It is not uncommon for controllers to take 5 years or more to be fully trained and certified.
The other reason is the technology available. Controllers can track every airplane in their sector using radar. The information is relayed to them from a small discrete box placed in most aircraft called a transponder. With the information from the transponder, controllers can monitor an airplane’s current position, it’s flight heading, and it’s altitude. Whenever aircraft enter into their domain, ATC will issue the pilot a ‘squawk code’ to manually enter into their transponder.
What is a squawk code? A squawk code is a four-digit code ATC gives pilots to manually enter into their transponders. Squawk codes can be used to identify aircraft type, as a way for ATC to keep track of individual flights, and as a means of communication in emergency situations.
An interesting note about squawk codes, each digit only goes up to seven, making only a total of 4096 codes. This is because, during the original designs, it took much more computer space to create digits up to nine than it did to seven.
Why are they called ‘squawk codes’?
During WWII, the allied forces using conventional radar were able to track their airplanes, though not very well. In addition to the mediocre radar picture, those on the ground had no way of distinguishing enemy aircraft from friendly forces.
In order to remedy this, the first transponders were created. These new transponders provided more quality radar information by receiving information and sending new information with an equally strong signal, instead of just bouncing the same signal off of an object. The new system was called Identification Friend or Foe (IFF) and was commonly called ‘Parrot’ due to its repeating nature. Thus, the secret codes pilots used to be identified on the ground were known as ‘squawk codes’.
In the 1950s, as air traffic was beginning to increase commercially, airports adopted the system of identifying aircraft and the old name for their codes stuck. Despite the many advances in technology since, the original transponder is very similar to what you’ll find in most airplanes today.
What do Squawk codes mean today?
Every aircraft flying through controlled airspace will be assigned a squawk code. Even those in uncontrolled airspace will often broadcast a code. When in uncontrolled airspace, the code is simply a designator for the type of flight, and not necessarily unique. For example, an airplane flying under Visual Flight Rules in the US will squawk 1200. At any given time, there are multiple 1200’s flying around.
So, is there any rhyme or reason to the other codes? For the most part, ATC simply follows a numeric order when assigning codes to aircraft. However, there are some interesting codes to note that differ depending on which country you’re flying through.
0000– In the US, this code as classified by the FAA as “to never be assigned” and for military intercept
0033– In the UK, this indicates the aircraft is engaging in parachute operations
5000– In Australia, this one is used for aircraft flying on military operations
7100– In Switzerland, 7100 is used for search and rescue
7777– in the US, Department of Defense interceptor aircraft on active air-defense missions and operating without ATC clearance in accordance with FAA Order 7610.4
Emergency Squawk Codes
There are also three codes drilled into every pilot’s head that are universal across the board.
7500, 7600, and 7700
These are the three squawk codes that every pilot begins learning immediately, regardless of where they fly. They are all unique emergency indicators, and accidentally or intentionally squawking them without need can have serious consequences.
7500 – is the international code for a hijacking. It is so that a pilot may discreetly notify ATC they have been hijacked, even if they cannot communicate this to them openly through the radio. The air traffic controller will verbally ask the pilot to ‘confirm squawk code’, to which the pilot can simply reply “affirmative”. At this point, ATC will closely monitor the flight and determine the next course of action. In some cases, military jets will be scrambled to escort the airplane.
7600 – Squawking 7600 is a way for pilots to let the tower know they do not have radio communications. The tower will then use light signals to communicate to the airplane on how and when to land. The airplane can respond in turn by rocking its wings.
7700 – This is the squawk code for a general emergency. This can mean the engine has shut off, a medical issue onboard, or something more minor like a primary system that isn’t working. 7700 is a code that is actually fairly commonly seen by ATC. Here’s why:
- By squawking 7700, the pilot is declaring an emergency. This opens all sorts of doors. First, ATC is going to announce to all other aircraft in the area that this aircraft is experiencing an emergency. This means that not only will everyone steer clear of the aircraft to give it room; they’ll also all be keeping an eye out for an emergency landing, which means a lot of accuracy in reporting a location for faster response.
- By declaring an emergency, the pilot of the aircraft can break any rule deemed prudent to minimize damage. The opportunity to fly a little faster or bank further than recommended isn’t the motivation for a pilot to declare an emergency, but it does take the edge off if a non-standard maneuver is going to be needed to land safely. An example could be an engine failure at low altitude, forcing you to land without ATC clearance. As long this is within the limits of emergency management, the pilot is full within their rights to do what is necessary
- It could just be a way of ensuring that ATC is fully aware that a serious situation is being dealt with onboard. In the fast-paced communication between pilots and tower control, sometimes the intent of information is missed. This could be minor, or in the case of some historical tragedies, it could be something major. An example of this is Avianca Flight 592, which ran out of fuel making routine flight patterns in 1990 because of a lack of understanding between the pilots and the control tower.
Summary
Squawk codes were initially created to identify friendly aircraft by the allied forces during WWII.
Today they are an integral part of aviation, both as a means of coordinating massive amounts of sky traffic and communication between the pilots and ATC.
Upon squawking an emergency situation, ATC and aircrews work together seamlessly as a result of their training to minimize damage to aircraft and loss of life.
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