List of X-planes

The X-planes are a series of experimental United States aircraft and rockets, used to test and evaluate new technologies and aerodynamic concepts. They have an X designator, which indicates the research mission within the US system of aircraft designations.

Most of the X-planes have been operated by the National Advisory Committee for Aeronautics (NACA) or, later, the National Aeronautics and Space Administration (NASA), often in conjunction with the United States Air Force. The majority of X-plane testing has occurred at Edwards Air Force Base.[1]

Some of the X-planes have been well publicized, while others, such as the X-16, have been developed in secrecy.[2] The first, the Bell X-1, became well known in 1947 after it became the first aircraft to break the sound barrier in level flight.[3] Later X-planes supported important research in a multitude of aerodynamic and technical fields, but only the North American X-15 rocket plane of the early 1960s achieved comparable fame to that of the X-1. X-planes 8, 9, 11, 12, and 17 were actually missiles[4]:14,15,17,18,24 used to test new types of engines, and some other vehicles were un-manned (some were remotely flown, some were partially or fully autonomous).

Most X-planes are not expected to go into full-scale production; one exception was the Lockheed Martin X-35, which competed against the Boeing X-32 during the Joint Strike Fighter Program, and has entered production as the F-35.[5]

Not all US experimental aircraft have been designated as X-planes; some received US Navy designations before 1962,[6] while others have been known only by manufacturers' designations,[N 1] non-'X'-series designations,[N 2] or classified codenames.[N 3]


List of X-planes
Type Manufacturer Agency Image Date Role Notes
X-1 Bell USAF, NACA 1946 High-speed and high-altitude flight First aircraft to break the sound barrier in level flight.
Proved aerodynamic viability of thin wing sections.[4]:5–7
Bell USAF, NACA 1951 High-speed and high-altitude flight
X-1E Bell USAF, NACA 1955 High-speed and high-altitude flight
X-2 Bell USAF 1952 High-speed and high-altitude flight First aircraft to exceed Mach 3.[4]:8
Douglas USAF, NACA 1952 Highly loaded trapezoidal wing Titanium alloy construction; Underpowered, but provided insights into inertia coupling.[4]:9
Northrop USAF, NACA 1948 Transonic tailless aircraft[4]:10
X-5 Bell USAF, NACA 1951 variable geometry First aircraft to fly with variable wing sweep.[4]:11
X-6 Convair USAF, AEC 1957 Nuclear Propulsion Not built. The Convair NB-36H was a B-36 modified to carry a nuclear reactor and flew from 1955 to 1957.[4]:12[7]
X-7 Lockheed USAF, USA, USN 1951 Ramjet engines.[4]:13
Aerojet NACA, USAF, USN 1949 Upper air research[4]:14 Later models used as sounding rockets.
Bell USAF 1949 Guidance and propulsion technology Assisted development of GAM-63 Rascal missile.[4]:15
X-10 North American USAF 1953 SM-64 Navajo missile testbed.[4]:16
X-11 Convair USAF 1957 SM-65 Atlas missile testbed.[4]:17
X-12 Convair USAF 1957 SM-65 Atlas missile testbed.[4][4]:18
Ryan USAF, USN 1955 Vertical takeoff and landing (VTOL) tailsitting VTOL flight.[4]:19
X-14 Bell USAF, NASA 1957 VTOL Vectored thrust configuration for VTOL flight.[4]:20
X-15 North American USAF, NASA 1959 Hypersonic, high-altitude flight First manned hypersonic aircraft; capable of suborbital spaceflight.[4]:21–22
X-15 A-2 North American USAF, NASA 1964 Hypersonic, high-altitude flight Major Pete Knight flew the X-15 A-2 to a Mach 6.70, making it the fastest piloted flight of the X-plane program.
X-16 Bell USAF 1954 High-altitude reconnaissance[4]:23 "X-16" designation used to hide true purpose.[8] Cancelled and never flew.
X-17 Lockheed USAF, USN 1956 High Mach number reentry.[4]:24
X-18 Hiller USAF, USN 1959 Vertical and/or short take-off and landing (V/STOL) Evaluated the tiltwing concept for VTOL flight.[4]:25
X-19 Curtiss-Wright Tri-service 1963 Tandem tiltrotor VTOL[4]:26 XC-143 designation proposed.[9]
Boeing USAF 1963 Reusable spaceplane Military missions.[4]:27 Cancelled and never built.
X-21A Northrop USAF 1963 Boundary layer control[4]:28
X-22 Bell Tri-service 1966 Quad ducted fan tiltrotor STOVL[4]:29
Martin Marietta USAF 1966 Maneuvering atmospheric reentry[4]:30 Designation never officially assigned.[10]
X-24A Martin Marietta USAF, NASA 1969 Low-speed lifting body[4]:31
X-24B Martin Marietta USAF, NASA 1973 Low-speed lifting body[4]:32
X-25 Bensen USAF 1955 Commercial light autogyro for downed pilots.[4]:33
Schweizer DARPA, US Army, USN
1967 Training glider for yaw-roll coupling
Quiet observation aircraft[4]:34
X-27 Lockheed None 1971 High-performance fighter[4]:35 Cancelled and never flew.
Sea Skimmer
Osprey USN 1970 Low-cost aerial policing seaplane[4]:36
X-29 Grumman DARPA, USAF, NASA 1984 Forward-swept wing[4]:37
Rockwell NASA, DARPA, USAF 1993 Single stage to orbit spaceplane[4]:38 Cancelled and never built.
X-31 Rockwell-MBB DARPA, USAF, BdV 1990 Thrust vectoring supermaneuverability[4]:39
X-32A Boeing USAF, USN, USMC, RAF 2000 Joint Strike Fighter[4]:40–41
X-32B Boeing USAF, USN, RAF 2001 Joint Strike Fighter[4]:40–41
Venture Star
Lockheed Martin NASA N/A Half-scale reusable launch vehicle prototype.[4]:42 Prototype never completed.
X-34 Orbital Sciences NASA N/A Reusable unmanned spaceplane.[4]:43 Never flew.
X-35A Lockheed Martin USAF, USN, USMC, RAF 2000 Joint Strike Fighter[4]:44–45
X-35B Lockheed Martin USAF, USN, USMC, RAF 2001 Joint Strike Fighter[4]:44–45
X-35C Lockheed Martin USAF, USN, USMC, RAF 2000 Joint Strike Fighter[4]:44–45
X-36 McDonnell Douglas NASA 1997 28% scale tailless fighter[4]:46
X-37 Boeing USAF, NASA 2010 Reusable orbital spaceplane[4]:47 Drop test performed in 2006. Five flights since 22 April 2010. (Four launches on Atlas V; one on Falcon 9.)
X-38 Scaled Composites NASA 1998 Lifting body Crew Return Vehicle[4]:48
X-39 Unknown USAF Classified Future Aircraft Technology Enhancements (FATE) program.[4]:49 Designation never officially assigned.[10]
X-40A Boeing USAF, NASA 1998 80% scale Space Maneuver Vehicle
X-37 prototype.[4]:50
X-41 Unknown USAF Classified Maneuvering re-entry vehicle.[4]:51
X-42 Unknown USAF Classified Expendable liquid propellant upper-stage rocket.[4]:52
Micro Craft NASA 2001 Hypersonic Scramjet[4]:53
Lockheed Martin USAF, NASA N/A F-22-based Multi-Axis No-Tail Aircraft thrust vectoring[4]:54 Cancelled, never flew.
X-45 Boeing DARPA, USAF
2002 Unmanned combat air vehicle (UCAV)[4]:55
X-46 Boeing DARPA, USN N/A Unmanned combat air vehicle (UCAV).[4]:56 Naval use. Cancelled, never flew.
X-47A Pegasus
Northrop Grumman DARPA, USN 2003 Unmanned combat air vehicle (UCAV)[4]:57 Naval use.
X-48 Boeing NASA 2007 Blended Wing Body (BWB)[4]:58
Piasecki US Army 2007 Compound helicopter
Vectored Thrust Ducted Propeller (VTDP) testbed.[11]
Boeing DARPA 2003 Canard Rotor/Wing[4]:60
Boeing USAF 2010[12] Hypersonic scramjet[13]
X-52 Number skipped to avoid confusion with Boeing B-52 Stratofortress.[10]
X-53 Boeing NASA, USAF 2002 Active Aeroelastic Wing[14]
X-54 Gulfstream NASA N/A Low-noise supersonic transport[15] in development.
X-55 Lockheed Martin USAF 2009 Advanced Composite Cargo Aircraft (ACCA)[16]
X-56 Lockheed Martin USAF/NASA 2012 Active flutter suppression and gust load alleviation Part of the high-altitude, long-endurance (HALE) reconnaissance aircraft program.[17]
ESAero/Tecnam NASA 2016 Low emission plane powered entirely by electric motors[18] Part of NASA's Scalable Convergent Electric Propulsion Technology Operations Research project[18] (SCEPTOR)
X-59 QueSST Lockheed Martin NASA 2018 Prototype quiet supersonic transport aircraft[19]
X-60A Generation Orbit Launch Services USAF 2018 Air-launched rocket for hypersonic flight research [20]
X-61A Dynetics USAF 2019 Gremlins air-launched and air-recoverable reconnaissance unmanned air vehicle (UAV)[21]

See also


  1. For example, the Piasecki PA-97
  2. For example, the NASA AD-1 and Bell XV-15
  3. For example, the Northrop Tacit Blue


  1. "X-Planes Experimental Aircraft". Federation of American Scientists. Retrieved 2012-06-01.
  2. Miller 2001, p. 209
  3. First Generation X-1 (fact sheet), Dryden: NASA, retrieved May 8, 2010.
  4. Jenkins, Landis and Miller 2003
  5. A history of the Joint Strike Fighter Program, UK: Martin-Baker, January 2010, archived from the original on 2010-12-30.
  6. "D-558-I" NASA Dryden Fact Sheets. NASA. Accessed May 8, 2010.
  7. Miller, J. The X-Planes, Speciality Press, 1983.
  8. "X-16". Global security, accessed 11 May 2010.
  9. Baugher 2007
  10. Parsch 2009, "Missing Designations"
  11. Parsch 2009, "DOD 4120.15-L"
  12. "X-51 Waverider makes historic hypersonic flight". US Air Force Public Affairs. 26 May 2010. Retrieved 27 May 2010.
  13. "X-51 Scramjet Engine Demonstrator - WaveRider" Accessed 2010-05-11.
  14. Jordan 2006
  15. 412015-L
  16. Kaufman 2009
  17. Norris 2012
  18. Harrington, J.D.; Kamlet, Matt; Barnstorff, Kathy (17 June 2016). "NASA Hybrid Electric Research Plane Gets X Number, New Name". NASA. Retrieved 17 June 2016.
  19. Jim, Banke (27 June 2018). "NASA's Experimental Supersonic Aircraft Now Known as X-59 QueSST". NASA. Retrieved 28 June 2018.
  20. "U.S. Air Force Designates GO1 Hypersonic Flight Research Vehicle as X-60A". 4 October 2018. Retrieved 4 October 2018.
  21. "Earthquake damage delays Gremlins trial". Flight International. 24 September 2019. Retrieved 28 October 2019.


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