What code is assigned to an aircraft when the pilot declares an emergency?

When a pilot declares an emergency, the assigned code is 7700. This transponder code is universally recognized as the emergency squawk code, which alerts air traffic control that the aircraft is in distress and requires immediate assistance.

The use of this code facilitates a faster response from air traffic controllers by drawing their attention to the aircraft's situation. Once the code is activated, it signifies various potential emergencies, from mechanical failures to medical emergencies on board.

In contrast, other codes have distinct purposes: for example, 7500 indicates a hijacking situation, while 7600 is used to communicate a radio failure. The code 7800 does not have a standard assignment within general aviation practices. Thus, understanding the significance of 7700 in emergency declaration contexts is crucial for effective communication and safety operations in aviation.