As used here, an experimental or research and development aircraft, sometimes also called an X-plane, is one which is designed or substantially adapted to investigate novel flight technologies.[1][2][3]
^Hygate, Barrie. British Experimental Jet Aircraft. Argus. 1990.
^Suturtivant, Ray. British Research and Development Aircraft. Haynes. 1990.
^Burney, Allan (Editor). British X-planes: The Jet Era. Aeroplane Illustrated: Aviation Archive Series. Key Aero. 2015.
