Squawk code · emergency

Squawk 7500: Unlawful interference

Squawk 7500 is the transponder code reserved for unlawful interference, meaning a hijacking.

Squawk 7500 is reserved for unlawful interference, the aviation term for a hijacking. It is the rarest of the three emergency codes. When it appears in public tracking data it is almost always a mis-set transponder or a test, and it is usually corrected within seconds or minutes.

What 7500 means

ICAO and the FAA (AIM 6-2-2 and 4-1-20) set aside code 7500 so a crew can silently alert controllers that the aircraft is under unlawful control. Controllers who see it follow a confidential procedure, which typically starts with a discreet radio check to confirm whether the code was intentional. Because it triggers such a significant response, pilots are trained to avoid selecting it by accident, for example by not passing through 7500 when changing codes.

Why you may see 7500 in flight data

Real hijackings are extremely rare. Far more often, a 7500 in a public data feed comes from one of these:

• A typo: a pilot entering 7550 or 5700, or confusing 7500 with the 7000 VFR code used in Europe.
• Ground testing: maintenance crews checking a transponder on the ramp.
• Decoding errors: a corrupted or misread message from a single receiver.

In these cases ATC confirms with the crew, the code is changed, and the flight continues. Public trackers often show the 7500 for only a few seconds.

How 7500 appears on heywhatsflying

Our emergencies now page lists any aircraft broadcasting 7500, 7600 or 7700 in the US snapshot. We show 7500 with a calm note, because the most likely explanation is a mis-set code. We do not speculate about individual flights, and neither should anyone else: the crew, controllers and authorities have far more information than a tracker does.

How common is it?

A genuine 7500 event in US airspace has not been a routine occurrence in decades. Mis-set or test 7500 readings show up in national data from time to time, perhaps a few times a month, and nearly always vanish quickly.

Common myths

• "A 7500 on a tracker means a hijacking is happening." Almost never. It most likely means a wrong code, and it is checked immediately by controllers.
• "Pilots dial 7500 out loud on the radio." The point of the code is that it is silent. Crews are trained not to discuss it openly.

Related codes: 7700 (general emergency), 7600 (lost communications), and 7000 (European VFR, a frequent source of confusion). Browse all codes on the squawk index.

Questions

Does squawk 7500 mean a hijacking?

It is the code reserved for unlawful interference, which includes hijacking. In public tracking data, though, a 7500 is almost always a mis-set code or a test and is corrected within seconds or minutes.

What happens when ATC sees 7500?

Controllers follow a confidential procedure that usually starts with a discreet check with the crew to confirm whether the code was set on purpose. If it was a mistake, the crew changes the code and the flight continues.

Should I report a 7500 I see on a tracker?

No. Controllers see the same code on their radar instantly and with far more context. Public data is delayed and can contain decoding errors.