FAA Aircraft Dispatcher Complete Practice Exam

True altitude refers to the vertical distance of an aircraft above mean sea level (MSL). This measurement is crucial for aviation safety and navigation because it provides a standardized reference point that is consistent regardless of local terrain or land features. By using mean sea level as a benchmark, all pilots and air traffic controllers can have a common understanding of the aircraft's altitude, which helps in maintaining safe separation between aircraft and avoiding terrain.

The concept of mean sea level accounts for variations in atmospheric pressure and sea levels, creating a reliable reference point for altitude measurements. This is especially important for flight planning and operational procedures, ensuring that all parties involved have accurate altitude information.

In contrast, height above ground level strictly measures the distance from the aircraft to the ground directly beneath it, which can vary widely with terrain. Height above the Earth's surface could refer to either mean sea level or ground level and lacks specificity. Height relative to the nearest city also does not provide a standardized measure as it varies with the city's elevation, making it unsuitable for navigation and safety in aviation.