Which airspace extends from 18,000 feet MSL up to and including FL 600, including waters within 12 NM of the coast and designated international airspace beyond 12 NM within areas of domestic navigational signal or ATC radar coverage?

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

Answer: (A)

Class A airspace is defined as the airspace from 18,000 feet MSL up to and including flight level 600. It includes waters within 12 nautical miles of the coast and designated international airspace beyond 12 NM where the United States provides navigational signals or ATC radar coverage. In this block, all operations require ATC clearance and are conducted under IFR; VFR flight is not permitted.

Other airspace types don’t match this altitude band. Class E typically sits below 18,000 MSL (though it can start at various lower bases), Class B surrounds major airports from the surface up to about 10,000 MSL, and Class G is uncontrolled up to the base of Class E.