A group of 1950s NACA research aircraft
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.  
GAF Pika – manned test craft for drone program France
Breguet-Dorand Gyroplane Laboratoire
SNECMA Coléoptère experimental tailsitter in 1959
Dornier Do 29 tilt rotor STOL
Heinkel He 178 pioneering turbojet-powered aircraft
Opel RAK.1 rocket engine research aircraft
Caproni-Campini N.1/CC.2 experimental
and second jet aircraft to fly
research aircraft in formation with Avro Vulcan bomber prototypes
Fairey Delta 2 research aircraft
Gloster E.28/39 jet engine research aircraft
Miles M.35 Libellula canard research aircraft
Rolls-Royce thrust measuring rig VTOL testbed
Bell X-1 supersonic research aircraft
Bell X-5 variable-sweep wing testbed
North American X-15 hypersonic rocket-powered research aircraft
Grumman X-29 forward swept wing and stability research aircraft
Other experimental types
high speed helicopter research aircraft
on ramp at NAA in Columbus, Ohio
high-altitude research aircraft – confirmed existence of jet stream
Lifting body research aircraft – from left to right, X-24A, M2-F3 and HL-10
Northrop N-9M flying wing
Vought V-173 disk wing research aircraft
^ 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.
http://1000aircraftphotos.com/Contributions/Visschedijk/7016.htm . Retrieved . 12 Aug 2015
Gibbs, Yvonne. "NASA Armstrong Fact Sheet: Lockheed JetStar Research Aircraft". NASA . Retrieved . 26 October 2019
Eckland, K.O. (2009-04-25). "Aerofiles Vought (Chance Vought), Lewis & Vought, Vought-Sikorsky". USA: Aerofiles.com . Retrieved . 20 September 2011
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