3−2−2. Class A Airspace a. Definition. Generally, that airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 nautical miles off the coast of the 48 contiguous States and Alaska; and designated international airspace beyond 12  nautical miles off the coast of the 48 contiguous States and Alaska within areas of domestic … [Read more...] about Class A Airspace