What is the minimum required altitude for flying in Class A airspace?

In Class A airspace, the minimum required altitude for flight is 18,000 feet Mean Sea Level (MSL). This designation is important because Class A airspace generally extends from 18,000 feet MSL up to and including 60,000 feet MSL. It is specifically designed for high-altitude flight operations and requires pilots to operate under instrument flight rules (IFR).

The regulation ensures that aircraft are safely separated by altitudes in this busy and high-density airspace, which is predominantly utilized by commercial airliners and is controlled by air traffic control. Therefore, any flight operating in Class A airspace must be at or above 18,000 feet MSL, maintaining safe vertical separation from other aircraft and adhering to the air traffic control requirements in that environment. This altitude requirement plays a critical role in ensuring safety in high-altitude operations and is fundamental knowledge for pilots.