What is pressure altitude?

Pressure altitude is defined as the vertical distance above the standard datum plane, which is a reference point used in aviation that corresponds to a specific air pressure, typically 29.92 inches of mercury (Hg) at sea level. This altitude provides a standard measure that allows pilots to ensure safe and consistent flight operations regardless of local weather conditions. It is calculated by setting the altimeter to the standard pressure setting.

By using the standard datum plane as a reference, pressure altitude becomes an important factor in aviation, especially when determining aircraft performance, as it directly relates to aircraft lift, engine performance, and the surrounding atmospheric conditions. This makes it crucial for pilots to understand and utilize pressure altitude when navigating and communicating with air traffic control.

The other options do not accurately define pressure altitude. While the altitude corrected for temperature (the first option) refers to density altitude, which is different, the altitude indicated by the altimeter at standard conditions (the third option) describes indicated altitude but does not encompass the broader concept of pressure altitude. The height of an aircraft relative to the ground (the fourth option) refers to absolute altitude, not pressure altitude.