Businesses in the aircraft and spacecraft category design, build, assemble, maintain or support vehicles that operate in the air or in space. Their work can include commercial and private aeroplanes, helicopters, gliders, unmanned aircraft, launch vehicles, satellites and other spacecraft. Some firms manufacture complete vehicles, while others supply components such as engines, airframes, avionics, navigation equipment, communications systems, sensors and specialist materials. Customers may also find engineering and technical services, including research and development, design, testing, inspection, repair and refurbishment. Aviation-related businesses can provide aircraft maintenance, component overhaul, modifications and technical support, while space-sector firms may develop satellite payloads, ground-control equipment or mission software.