Class A Airspace
Class A is generally the Airspace of 18,000 ft mean sea level (MSL) up to and including flight level (FL) 600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States, and Alaska. Unless otherwise authorized, all operations in Class A are conducted under instrument flight rules (IFR). Pilots operating in Class A airspace must conduct that operation under IFR and only under ATC clearance received prior entering the airspace. Unless otherwise authorized by ATC, each aircraft operating in Class A airspace must be equipped with a two-way radio capable of communication with ATC on a frequency assigned by ATC. Unless otherwise authorized by ATC, all aircraft within Class A airspace must be equipped with the appropriate transponder equipment meet all applicable specifications found in 14 CFR section 91.215.