Which items must be monitored continuously according to ATC procedures?

In the context of air traffic control procedures, continuous monitoring of interphones and assigned radio frequencies is essential. This allows air traffic controllers to maintain constant communication with pilots and other relevant personnel. By doing so, controllers can provide timely instructions, convey critical information about flight safety, and address any ongoing situations that may arise during operations. Monitoring assigned frequencies enables seamless coordination and quick responses to emergencies or changes in flight plans.

While other choices might involve important aspects of air traffic management, they do not all require continuous monitoring in the same direct way. For example, while flight plans and aircraft positions are crucial for situational awareness, these do not need to be monitored in real-time on the same level as active communications via interphones and radio frequencies. Similarly, while monitoring weather and radar reports is vital for overall air traffic safety, it typically involves scheduled updates rather than continuous live communication. Lastly, while staying alert to pilots and flight crews is important for safety, it is achieved mainly through the continuous communication channels established via interphones and radio frequencies. Thus, continuous monitoring of interphones and assigned radio frequencies is fundamentally critical for effective air traffic control operations.