The international emergency transponder code (squawk code) for a hijacking or "unlawful interference" is 7500. When a pilot enters this four-digit code into the aircraft's transponder, it immediately triggers an alarm on the air traffic controller's radar screen, identifying the flight as being under threat without the need for verbal radio communication. This "silent alarm" is critical in situations where a hijacker may be monitoring the cockpit's radio transmissions. Once 7500 is squawked, ATC will acknowledge the signal with a discreet "Confirm squawk 7500" to ensure it wasn't an accidental entry. If confirmed, a high-level security protocol is initiated: the aircraft is given absolute priority, and military authorities are notified to begin an aerial intercept and escort. This code is part of a "special three" used globally: 7500 for hijacking, 7600 for radio communication failure ("lost comms"), and 7700 for a general life-threatening emergency. In 2026, modern avionics have added "One-Touch" emergency buttons that can instantly broadcast 7500 to the nearest ground station and satellite tracking systems simultaneously.