Which transponder code indicates a loss of communication?

The transponder code that indicates a loss of communication is 7600. This code is specifically assigned to alert air traffic control and other aircraft that the aircraft is experiencing communication difficulties. When a pilot sets their transponder to 7600, it serves as a clear signal that they cannot receive or transmit radio communications, enabling air traffic controllers to provide assistance and take appropriate actions.

While other codes serve different purposes, such as 7700 for emergencies and 7500 for unlawful interference (hijacking), it is the 7600 code that directly relates to communication failures. This distinction is crucial for maintaining safety and situational awareness in controlled airspace. Understanding the significance of these codes is essential for pilots to effectively convey their operational status and respond appropriately in various situations.