In what units is aircraft altitude typically measured?

Aircraft altitude is typically measured in feet or meters above sea level due to the standard practices and conventions established in aviation. Feet are primarily used in the United States and many other countries for operational reasons, particularly in air traffic control and pilot communications, where quick and clear understanding of altitude is critical for safety. In contrast, meters are more commonly used in other parts of the world, particularly in countries that adhere to the International Civil Aviation Organization (ICAO) standards.

Using feet facilitates precise altitude reporting, which is essential for maintaining separation between aircraft, especially when flying at higher altitudes where airspace becomes crowded. Meters, while less common in certain regions, are equally effective in providing an accurate altitude reference. Both measurements serve the purpose of providing pilots and air traffic controllers with necessary information to ensure safe flight operations.

Other units mentioned in the options, such as nautical miles, are typically used for measuring distances over the ground rather than altitude. Yards, while a unit of measurement, are not standard in aviation for indicating altitude, and kilometers above sea level, although technically a possible measure, have not been widely adopted in aviation practice for altitude reporting purposes.