How often must air traffic controllers monitor the ATC frequency?

Air traffic controllers are responsible for maintaining safe and efficient air traffic operations, which requires constant communication with pilots and other controllers. Monitoring the ATC frequency continuously until relieved by another controller ensures that they are always aware of the current situations, updates, and any emergencies that may arise. This continuous monitoring allows for timely responses to dynamic changes in air traffic, ensuring that safety is prioritized at all times.

In contrast, options suggesting limited or intermittent monitoring, such as only during peak hours or just at the start of each operational day, could lead to hazardous situations where vital information is missed. Controllers must be vigilant and responsive throughout their entire shift to manage the flow of air traffic effectively and to react immediately if an issue arises.