what is 7700 squawk

When a plane "squawks 7700," it means that the crew has declared an emergency situation. Squawk codes are assigned to a flight before departure, and the four digits can be between zero and seven, giving 4,096 possible combinations. Squawking 7700 is used in particular situations when an aircraft wants to communicate something to air traffic control (ATC) urgently, such as engine failure, pressurization problems, other technical problems, or urgent medical emergencies. By resetting their transponder to the emergency code of 7700, all ATC facilities in the area are immediately alerted that the aircraft has an emergency situation. This allows ATC to prepare for a quick landing, inform nearby aircraft, clear any runways needed, and inform the authorities of any other support necessary, such as fire services or an ambulance.