The Classic Aero AES Subsystem (CAAS) software implements the core of an Inmarsat Aircraft Earth Station (AES) as defined in the Inmarsat Aeronautical System Definition Manual (SDM). The Inmarsat Aero system provides communications for passengers, airline administration, aircraft operational control and air traffic control services (safety services). Over 8,000 aircraft, including almost all of the world’s long haul aircraft, are fitted with Classic Aero terminals.