ENGINERING SERVICES IN AIRCRAFT, COMMERCIAL, AND INDUSTRIAL FIELDS INCLUDING RESEARCH AND STUDIES RELATING TO ELECTRICAL MECHANICAL, METALLURGICAL, PNEUMATIC, AERODYNAMIC, AND THERMODYNAMIC PROBLEMS; AND DESIGN, DEVELOPMENT, AND TESTING OF EQUIPMENT APART FROM THE MANUFACTURE AND SALE OF ITS PRODUCTS; AND THE OVERHAULING, RECONDITIONING, AND MODIFYING OF AIRCRAFT FOR THE PUBLIC