High Quality Content by WIKIPEDIA articles! The British Aerospace 125 is a twin-engined mid-size corporate jet, with newer variants now marketed as the Hawker 800. It was known as the Hawker Siddeley HS.125 until 1977. It was also used by the British Royal Air Force as a navigation trainer (as the Hawker Siddeley Dominie T1) until January 2011, and was used by the United States Air Force as a calibration aircraft (as the C-29).