What is the pressure altitude?

Pressure altitude is defined as the altitude indicated on the altimeter when it is set to a standard atmospheric pressure setting of 29.92 inches of mercury (inHg). This measurement is crucial for pilots, as it allows them to gauge their altitude in relation to standard atmospheric conditions. By using this setting, pilots can ensure that their altitude readings are consistent, regardless of the local pressure conditions that might affect their altimeter.

This concept is essential for navigation, indicating aircraft performance, and when flying in controlled airspace, as it helps maintain safe separation between aircraft by providing a common reference point. The other options do not accurately describe pressure altitude, focusing instead on different aspects of altitude measurement or flight operation.