Airspace from 18,000 feet MSL up to and including FL 600 including waters within 12 NM of coast of the 48 contiguous states and Alaska, and designated international airspace beyond 12 NM within areas of domestic radio navigational signal or ATC radar coverage is which class?

• A. Class B
• B. Class A
• C. Class E
• D. Class G

Answer: (B)

High-altitude, instrument flight rules operations define this airspace. In the United States, the block from 18,000 feet MSL up to and including FL600 is designated Class A. It includes the airspace over the continental U.S., Alaska, waters within 12 nautical miles of the coast, and designated international airspace beyond 12 NM where domestic radar coverage exists. The key requirement here is that entry into Class A requires ATC clearance and the flight must be conducted under an IFR flight plan; VFR operation is not permitted there. This combination of a specific altitude band and mandatory IFR/clearance is what makes it Class A. Other classes operate at different altitudes and around airports, so they don’t match this high-altitude, IFR-only block.