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Squawk code · reserved

Squawk 0000: No code / non-standard

Squawk 0000 is not assigned for normal civil use; in public data it usually means no code is set or the value is an artifact.

Squawk 0000 is not a normal civil code. When you see it in public flight data, it most often means a transponder with no code entered, a test, or a data artifact. Some military operators also use it.

What 0000 means

Civil air traffic control in the US does not assign 0000 to flights. The FAA's code allocation plan treats it as a non-discrete code outside normal use, and the AIM does not list it for pilots. Elsewhere it has had various specialized uses, including some military operations. In other words, there is no single public meaning, which is exactly why it is worth handling calmly.

Why you see 0000 in tracking data

  • No code set: some ADS-B systems report 0000 when the pilot hasn't entered a code, for example on the ground right after power-up.
  • Ground vehicles and test units: ADS-B-equipped airport vehicles and test transmitters may report 0000.
  • Military use: some military aircraft fly with 0000 in specific operations.
  • Decoding gaps: some feeds show 0000 where the squawk simply has not been received yet.

How 0000 appears on heywhatsflying

We do not treat 0000 as an emergency or anything alarming. On the live map such aircraft display normally. If a military-looking aircraft shows 0000, it may appear on military and government now, which uses type, callsign and address patterns rather than squawk alone.

Squawk versus no squawk

A blank squawk and 0000 are not the same thing in most data feeds. A blank (shown on our pages as a dash) means no squawk value has been received at all, which is common for aircraft heard only briefly or via sources that don't include the code. A 0000 means a value was received and it was all zeros. Either way, the aircraft's other data, such as hex address, altitude and speed, is still valid and usually more informative.

Related codes: 4000, 7777 and 2000. Learn more in how to read flight data or see the squawk code index.

Questions

What does squawk 0000 mean?

It is not assigned for normal civil flights. In public data it usually means no code has been set, a test transmitter, a data artifact, or occasionally a military operation.

Is squawk 0000 an emergency?

No. The emergency codes are 7700, 7600 and 7500. A 0000 code on its own says nothing about the state of a flight.