What is pressure altitude?

Pressure altitude is defined as the altitude above the standard datum plane, which is set at a standard atmospheric pressure of 29.92 inches of mercury (Hg) at sea level. This measurement is significant in aviation because it provides a standardized reference point for pilots and air traffic controllers, allowing for consistent altitude reporting and separation of aircraft.

When flying, measuring altitude relative to this standard pressure is essential for ensuring safe altitude separation between aircraft. Since atmospheric pressure decreases with an increase in altitude, the standard datum plane helps pilots understand their aircraft's actual altitude in relation to the pressures they would encounter at various heights, facilitating more accurate navigation and altitude assignment.

The other options do not accurately define pressure altitude. While altitude above mean sea level or cruising flight altitude can be relevant concepts, they do not specifically relate to the adjustments made for atmospheric pressure. Similarly, altitude adjusted for temperature deviations pertains more to density altitude than to pressure altitude itself.