What is the required action for a pilot when transitioning from day to night operations?

When transitioning from day to night operations, the pilot is required to turn on navigation (NAV) lights. This action is important as it enhances the visibility of the aircraft to other pilots and ground personnel, thereby improving safety during nighttime operations. NAV lights are essential during night flying because they allow for better orientation and situational awareness, helping other aircraft to identify and maintain safe distances.

While other choices may pertain to different safety protocols or operational procedures, turning on the NAV lights is specifically mandated to ensure that an aircraft is conspicuous and complies with regulations that enhance nighttime visibility. Whether other actions, such as filing a flight plan or completing a flight review, might be prudent or required in specific situations, they are not directly related to the immediate transition from day to night operations as NAV lights are.