Final answer:
When pilots lose sight of the airfield or runway environment, they rely on instruments, procedures, and training to navigate and land safely.
Step-by-step explanation:
When a pilot loses sight of the airfield environment (NAS) or the runway environment (ICAO), they rely on instruments to navigate and land safely.
For instance, they may use radar instruments, such as the altimeter, to determine their altitude, or the instrument landing system (ILS) to guide them down to the runway.
Pilots are also trained to rely on their training and knowledge of procedures to handle situations where visibility is poor, such as executing missed approaches or diverting to an alternate airport.