What is the highest priority for interphone transmission?

The highest priority for interphone transmission is emergency messages. In air traffic control communications, the primary concern is the safety of the aircraft and its occupants. When an emergency arises, whether due to a medical issue, technical malfunction, or other urgent situations, the information needs to be transmitted immediately to ensure prompt assistance and effective coordination.

Emergency messages take precedence over routine communications such as clearances, control instructions, movement messages, and flight plans. The rationale is that during an emergency, the swift exchange of critical information can significantly impact the outcome and safety of the flight. Therefore, ensuring that emergency situations are communicated with priority reflects the fundamental imperative in aviation to protect lives and maintain safe operations. This priority ensures that air traffic controllers and pilots can respond effectively to any life-threatening or hazardous situation that may arise.