What is the main purpose of using a local pressure setting during flight?

The main purpose of using a local pressure setting during flight is to accurately determine altitude and ensure safety. When pilots set the altimeter to a local barometric pressure, they can effectively calibrate the instrument to reflect true altitude above sea level. This is crucial in maintaining safe vertical separation from other aircraft and avoiding terrain.

Using the current pressure setting ensures that the altitude readings are accurate, which is particularly important in areas with rapidly changing weather conditions or when flying at low altitudes where terrain avoidance is critical. A miscalibrated altimeter can result in either an incorrect altitude reading or a dangerous situation, especially in mountainous regions where altitude awareness is vital.

While the other options have their own importance in aviation, they do not directly address the primary reason for adjusting the local pressure setting in the altimeter. For instance, cabin pressure maintenance is more relevant to pressurized aircraft rather than the altimeter setting itself. Adjusting for temperature changes and saving fuel consumption involve different operational procedures and considerations that do not directly pertain to the local pressure setting of the altimeter.