Altitude is expressed in which of the following formats in aviation phraseology?

In aviation phraseology, altitude is most commonly expressed in terms of flight levels and feet above sea level (ASL). Flight levels represent altitude in hundreds of feet above a standardized pressure level, typically 29.92 inches of mercury. This system allows for a uniform reference point for various aircraft operating at different altitudes, particularly when flying at high altitudes in controlled airspace.

Feet ASL can also be given in thousands plus hundreds, where for example, 6,500 feet might be stated as "six thousand five hundred." This method ensures clarity in communication between pilots and air traffic control, contributing to safety and efficiency in flight operations.

Usage of kilometers above sea level does occur in some regions, but it is not the predominant system in aviation phraseology, especially in the United States, where the feet ASL and flight levels are the standard. Similarly, expressing altitude in statute miles is not standard in aviation as it does not provide the precision required for safe navigation and control of aircraft.