Page "Aircraft hijacking" Paragraph 17

To communicate to air traffic control that an aircraft is being hijacked, a pilot under duress should squawk 7500 or vocally, by radio communication, transmit "( Aircraft callsign ); Transponder seven five zero zero.

" This should be done when possible and safe.

An air traffic controller who suspects an aircraft may have been hijacked may ask the pilot to confirm " squawking assigned code.

" If the aircraft is not being hijacked, the pilot should not squawk 7500 and should inform the controller accordingly.

A pilot under duress may also elect to respond that the aircraft is not being hijacked, but then neglect to change to a different squawk code.

In this case, the controller would make no further requests and immediately inform the appropriate authorities.

A complete lack of a response would also be taken to indicate a possible hijacking.

Of course, a loss of radio communications may also be the cause for a lack of response, in which case a pilot would usually squawk 7600 anyway.