Establishments primarily engaged in manufacturing aircraft parts and auxiliary equipment, not elsewhere classified. This industry also includes establishments owned by manufacturers of aircraft parts and auxiliary equipment and primarily engaged in research and development on aircraft parts, whether from enterprise funds or on a contract or fee basis. Establishments primarily engaged in manufacturing or assembling complete aircraft are classified in Industry 3721; those manufacturing aircraft engines and parts are classified in Industry 3724; those manufacturing aeronautical instruments are classified in Industry 3812; those manufacturing aircraft engine electrical (aeronautical electrical) equipment are classified in Industry 3694; and those manufacturing guided missile and space vehicle parts and auxiliary equipment are classified in Industry 3769. Establishments not owned by manufacturers of aircraft parts but primarily engaged in research and development on aircraft parts on a contract or fee basis are classified in Services, Industry 8731.