What phrase should be used to interrupt lower priority messages for emergencies?

The phrase "Break for emergency" is specifically designed to signal the urgency of an emergency communication while effectively interrupting lower priority messages. In air traffic control communication, it's vital to have a clear and standardized way to indicate that an emergency situation is occurring and that immediate attention is required. Using this phrase specifies that an urgent matter needs to be addressed promptly, thereby prioritizing the emergency message.

Other options might not convey the same sense of urgency or could lead to confusion. For example, "Standby for emergency" might imply that something is coming but does not clearly indicate that the situation is immediate. "Attention all units" often signifies a general broadcast, which may not effectively interrupt ongoing communications. Similarly, "Clear the frequency" could be interpreted differently in terms of who should clear channels or might not sufficiently express that an emergency is taking precedence. The term "Break for emergency" uniquely captures the need for immediate attention and action, making it the appropriate choice in such critical situations.