What must pilots refer to when determining altered minimum flight levels during flights?

Pilots must refer to altimeter settings when determining altered minimum flight levels during flights because the altimeter directly affects altitude readings. Accurate altitude readings are crucial for maintaining safe separation from terrain and other aircraft. When flying at high altitudes, pilots need to ensure that their altimeter is calibrated correctly to local atmospheric pressure, which can vary based on weather conditions. This calibration allows the aircraft to maintain the proper altitude relative to a reference point, ensuring compliance with minimum flight level requirements.

Understanding altimeter settings is essential in altering flight levels, as discrepancies in pressure can lead to flying at an unsafe altitude. While factors like weather conditions can influence flight operations, and aircraft dimensions can affect performance, it is the altimeter settings that specifically dictate the continuous and precise altitude management required throughout a flight.