Understanding Squawk Codes and How They Work

Air traffic has increased in recent decades. At any given moment, there are approximately 8,000 to 12,000 airplanes flying in the United States. To safely guide these airplanes and minimize the risk of collision, Air Traffic Control (ATC) assigns each of these airplanes a unique code known as a squawk code.

What Is a Squawk Code?

A squawk code is a four-digit number given to airplanes by ATC. Also known as a transponder code, it’s used to identify and track airplanes. Airplanes have transponder systems that send their respective squawk codes to nearby radars.

During the early years of aviation, airplanes didn’t have squawk codes. There were still radar systems available to track airplanes, but there wasn’t a way to identify and distinguish between the different airplanes in the air. This prompted aviation authorities to develop squawk codes.

How Squawk Codes Work

Squawk codes aren’t static. Rather, they are generated and assigned by the ATC. The ATC will generate a unique squawk code when an airplane enters its airspace. While communicating with the pilot, the ATC will provide this squawk code. The pilot will then enter the squawk code into the airplane’s transponder.

Once entered into the transponder, the airplane will constantly send out its squawk code. The ATC will be able to see the airplane’s squawk code on radar. As a result, the ATC will know the exact location of the airplane as long as it remains in the ATC’s airspace.

Squawk Code Structure

Squawk codes typically range from 0000 to 7777. There are several different types of squawk codes, however, each of which has its own structure.

Visual Flight Rules (VFR) squawk codes are assigned to airplanes in uncontrolled airspace. In the United States and Canada, airplanes flying in uncontrolled airspace typically use a VFR squawk code of 1200.

Instrument Flight Rules (IFR) squawk codes, as the name suggests, are intended for airplanes under instrument flight rules. This is the most common type of squawk code. Commercial airplanes, as well as many private airplanes, use an IFR squawk code. IFR squawk codes are assigned by the ATC and used to identify airplanes.

There are also special purpose squawk codes. They still consist of a four-digit number, and they are still used for the purpose of identifying airplanes. Special purpose squawk codes, though, are used in special situations. If an airplane is experiencing a midair emergency and needs to land, for instance, the ATC may assign it a special purpose squawk code. Alternatively, airplanes that experience communication failure may use a special purpose squawk code.

Looking to Build Your Own Airplane?

Click below to browse Monroe's Aerospace Parts!

Browse Aerospace Parts