True altitude

• A. Actual height above mean sea level (MSL)
• B. Indicated altitude corrected for temperature
• C. Altitude above the standard datum plane
• D. Height above the Earth's surface

Answer: (A)

True altitude is the actual height of the aircraft above mean sea level. This is the real vertical distance from the aircraft to MSL, regardless of what your instrument shows or how the atmosphere varies. The altimeter indicates altitude based on air pressure, but weather conditions and instrument factors can make that reading differ from the true altitude. In practice, you can adjust indicated altitude for temperature and other nonstandard conditions to estimate true altitude, but the fundamental definition remains the height above mean sea level. The other options describe height relative to different references or general height above the surface, not the standard aviation meaning of true altitude.