Plain English Meaning

Class A is the high-altitude airspace that begins at 18,000 feet and goes up to 60,000 feet. Every flight inside it must be on an IFR clearance with ATC -- there is no VFR flying allowed in this airspace.

Full Definition

Class A is a category of regulated airspace in the United States extending from 18,000 feet MSL up to and including Flight Level 600 (60,000 feet), over the 48 contiguous states, Alaska, and the airspace overlying the waters within 12 nautical miles of the coast. All operations within Class A airspace must be conducted under Instrument Flight Rules (IFR), and aircraft must be on an IFR clearance from Air Traffic Control. Pilots must an , and aircraft must be appropriately equipped for .