Squawk 7500: What the Hijack Code Means, and Why It Is Usually a Mistake

What the code means
How controllers respond
Why most 7500s are mistakes
The emergency codes
Recent events

What the code means

7500 is reserved for unlawful interference: a hijacking or a threat against the aircraft. Its value is that a crew can raise the alarm silently, with four digits on the transponder, without saying anything on a frequency that others can hear.

How controllers respond

Controllers do not ask about it openly. They follow a separate protocol: they confirm discreetly, notify the agencies that need to know, and give the flight whatever it requests. In the US, military aircraft may be sent to escort it.

Why most 7500s are mistakes

A crew dialling a new code, or reaching for 7700 or 7600, can pass through 7500 for a moment. Controllers then ask the crew to confirm the code, and the flight carries on. Cockpit labels these events "Squawking 7500", never "hijack", and only shows them after the code has been held and confirmed.

On a transponder, 7500 is one digit away from 7600 and 7700, and the knobs turn through it.

7700, 7600, 7500 and 1200

7700
General emergency.
Any problem the crew considers serious enough to need priority. The flight usually keeps talking to ATC.
7600
Radio failure.
The aircraft can fly normally but cannot transmit or receive. It continues on its last clearance and lands using light signals from the tower.
7500
Unlawful interference.
A hijacking or a threat on board. Controllers follow a separate protocol. Rare, and often set by mistake while dialling 7600 or 7700.
1200
VFR.
Not an emergency. The default code for aircraft flying visually in the US without a controller assignment.