What does the term 'altitude' specifically refer to in aviation?

The term 'altitude' in aviation specifically refers to the vertical distance of the aircraft above a reference point, typically above sea level or the ground. This concept is crucial for pilots and air traffic control to ensure safe flight operations, navigation, and separation between aircraft.

In aviation, altitude can be measured in several ways, such as altitude above sea level (MSL - Mean Sea Level) or altitude above the ground (AGL - Above Ground Level). Understanding altitude is essential for maintaining safe distances in the air and for effective communication between pilots and air traffic controllers.

While atmospheric pressure at sea level is an important concept in aviation, it does not define altitude itself. Similarly, horizontal distance covered during flight pertains to distance traveled rather than height, and the speed of the aircraft relates to its velocity and is not a measure of altitude. Each of these elements plays a role in aviation but does not encapsulate what altitude specifically means in this context.