Why is it important to adjust the altimeter during flights?

Adjusting the altimeter during flights is crucial for ensuring accurate pressure readings. The altimeter measures altitude by comparing the atmospheric pressure at the aircraft's location to a standard pressure value. As the aircraft climbs or descends, the ambient pressure changes, and to reflect the true altitude of the aircraft, the altimeter must be adjusted accordingly.

If the altimeter is not accurately set to the local pressure, it could lead to incorrect altitude readings, which may affect safety and navigation. For example, flying at an inaccurate altitude could result in a dangerous situation, such as a collision with terrain or other aircraft. Therefore, constantly adjusting the altimeter based on current pressure conditions is vital for maintaining safe and accurate flight operations.

The other options relate to different aspects of flying but do not address the primary function of the altimeter, which is to gauge altitude based on pressure variations in the atmosphere.