X-planes •
Bell X-1 – Supersonic flight and sound barrier •
Bell X-2 – Mach 2–3 supersonic flight •
Douglas X-3 Stiletto – Sustained supersonic flight •
Northrop X-4 Bantam – Tailless aircraft •
Bell X-5 – Variable-sweep wing •
Convair X-6 – Nuclear reactor test aircraft (for nuclear-powered aircraft) •
Lockheed X-7 – Unmanned ramjet and guidance test missile •
Aerojet General X-8 – Sounding rocket (became
Aerobee) •
Bell X-9 Shrike – Guided missile •
North American X-10 – Unmanned missile technology demonstrator •
Convair X-11 – Single engine missile testbed for
Atlas •
Convair X-12 – Three engine missile testbed for
Atlas •
Ryan X-13 Vertijet – Tail sitter VTOL jet •
Bell X-14 –
Thrust vectoring VTOL jet •
North American X-15 – Hypersonic rocket-powered research aircraft (Mach 6) •
Bell X-16 - High-altitude reconnaissance jet •
Lockheed X-17 – Research rocket testing high mach re-entry •
Hiller X-18 – Tiltwing STOVL cargo aircraft •
Curtiss-Wright X-19 – VTOL tiltrotor •
Boeing X-20 Dyna-Soar – Spaceplane program •
Northrop X-21 – Laminar flow wing •
Bell X-22 – Ducted fan V/STOL •
Martin X-23 PRIME – Lifting body reentry vehicle testbed •
Martin Marietta X-24 – Lifting body test aircraft •
Bensen X-25 – Single-seat autogyro •
Schweizer X-26 Frigate – Sailplane •
Lockheed X-27 Lancer – high-performance technology demonstrator based on
Lockheed CL-1200 •
Pereira X-28A Sea Skimmer – Single-seat flying boat for US Navy •
Grumman X-29 – Forward-swept wing test aircraft •
Rockwell X-30 – Single-stage-to-orbit spacecraft •
Rockwell-MBB X-31 – Extreme angle of attack test aircraft •
Boeing X-32 –
Joint Strike Fighter Program technology demonstrator •
Lockheed Martin X-33 – Unmanned scale demonstrator for
VentureStar single stage to orbit spacecraft •
Orbital Sciences X-34 – Reusable launch vehicle testbed •
Lockheed Martin X-35 –
Joint Strike Fighter Program technology demonstrator, developed into
F-35 Lightning II •
McDonnell Douglas X-36 – Tailless fighter research agility aircraft •
Boeing X-37 – Reusable unmanned spacecraft •
NASA X-38 – Crew return vehicle for
International Space Station (cancelled after tests) •
X-39 – Reserved for USAF/DARPA program use •
Boeing X-40 Space Maneuver Vehicle – Testbed for X-37 guidance and flight characteristics •
X-41 Common Aero Vehicle – Classified DARPA/NASA maneuvering re-entry vehicle •
X-42 Pop-Up Upper Stage – Classified rocket upper stage •
NASA X-43 Hyper-X – Hypersonic scramjet •
Lockheed Martin X-44 MANTA – Multi-axis tailless aircraft concept •
Boeing X-45 – Unmanned combat air vehicle •
Boeing X-46 – Unmanned combat air vehicle (proposal only) •
Northrop Grumman X-47A Pegasus – Unmanned combat air vehicle •
Northrop Grumman X-47B Iron Raven – Aircraft carrier capable unmanned combat air vehicle technology demonstrator •
Boeing X-48 – Blended wing aircraft •
Piasecki X-49 – Compound helicopter technology demonstrator •
Boeing X-50 Dragonfly – Gyrodyne unmanned aerial vehicle •
Boeing X-51 Waverider – Mach 5+ scramjet missile demonstrator •
Boeing X-53 Active Aeroelastic Wing – Wing warping flight demonstrator •
Gulfstream X-54 – Supersonic boom intensity research and demonstration aircraft •
Lockheed Martin X-55 – Advanced composites technology demonstrator •
Lockheed Martin X-56 –
Flutter suppression and gust load testing unmanned testbed •
NASA X-57 Maxwell - Electric-powered light aircraft •
Lockheed Martin X-59 QueSST - Low-boom supersonic aircraft •
Generation Orbit X-60 - Air-launched single stage suborbital rocket vehicle •
Dynetics X-61 Gremlins - Unmanned aerial vehicle •
General Dynamics X-62 VISTA - Variable stability, thrust vectoring (formerly known as NF-16D VISTA) •
ABL Space Systems X-63 -
Aerospike variant of RS1 rocket booster •
Invocon X-64 - Recoverable suborbital rocket •
Aurora X-65 CRANE -
active flow control demonstrator •
Boeing X-66 -
Truss-Based Wing demonstrator
Other experimental types high speed helicopter research aircraft on ramp at NAA in Columbus, Ohio in flight during 2002 for
US Department of Energy ARM-
UAV program •
Acme Sierra 1959 – Technology demonstrator •
AstroFlight Sunrise 1974 – Solar powered drone •
Ball-Bartoe Jetwing 1977 – Blown wing research •
Bell D-292 1985 – Advanced Composite Airframe Program •
Bell L-39 1946 – Swept wing research •
Bell Model 65 1954 – Tiltjet
VTOL •
Bell XV-15 1977 –
Tiltrotor VTOL, precursor to
V-22 Osprey •
Bell 533 1962 – US Army high speed helicopter experiments • Boeing
ecoDemonstrator 2012 – Airliner fuel efficiency and noise reduction technologies •
Budd BB-1 Pioneer 1931 – Stainless steel construction •
Burnelli RB-1 1921 – Lifting body proof of concept vehicle •
Carlson-Lynch Vertipactor 1923 – Wingless VTOL aircraft •
Chrysler VZ-6 1959 – Ducted fan •
Convair NB-36 1955 – Nuclear propelled aircraft testbed •
Convair XFY Pogo 1954 – Fixed propeller VTOL •
Curtiss-Wright VZ-7 1958 –
Quadcopter •
Curtiss-Wright X-100 1963 – Tilt rotor VTOL (developed into X-200 and X-19) •
Custer Channel Wings 1953 – Blown half-barrel wings •
Doak VZ-4 1958 – Tilt-fan VTOL •
Douglas D-558-I Skystreak 1947 – Supersonic research •
Douglas D-558-II Skyrocket 1948 – Supersonic research •
Fairchild VZ-5 1959 – Deflected air VTOL •
Farrar LSG-1 Bird Flight Machine 1969 – Glider to research bird flight high-altitude research aircraft – confirmed existence of jet stream •
General Dynamics F-16XL 1982 – Relaxed stability delta wing, boundary layer suction laminar flow •
General Dynamics F-16 VISTA 1992 – Variable stability, thrust vectoring (Redesignated X-62 Vista in 2021) •
General Electric GE36 testbed 1986 – Propfan engine testbed on a modified
Boeing 727 •
Goodyear Inflatoplane 1956 – Inflatable rescue aircraft technology demonstrator •
Gossamer Albatross 1979 – Human-powered flight •
Gossamer Condor 1977 – Human-powered flight • modified
Grumman Gulfstream II – Engine testbed for the NASA Propfan Test Assessment (PTA) •
Hiller VZ-1 Pawnee 1955 – Direct lift rotor platform •
Hypersonic Technology Vehicle 2 2010 – Hypersonic glider •
Kaman K-125 1947 – Intermesh twin rotor helicopter, servo-flap control •
Kaman K-16 – Modified
Grumman Goose for tiltwing V/STOL research •
Lockheed Altair 1938 – Twinned engine testbed (both engines were in a single cowl) • NASA Dryden
Lockheed C-140 Jetstar 1964 – Electronic variable stability,
propfan engine (1981) and
laminar flow wing testbed (1985) •
Lockheed Have Blue – Stealth technology demonstrator •
Lockheed Vega Winnie Mae – high-altitude research – confirmed existence of jet stream •
Lockheed QT-2 – Quiet Thruster noise suppression experiments •
Lockheed XC-35 – Pressurized cabin development •
Lockheed XV-4 Hummingbird – Jetlift VTOL •
LTV XC-142 – VTOL transport technology demonstrator •
Martin 162A Tadpole Clipper – Proof of concept aircraft •
Martin XB-26H Marauder – Tandem undercarriage •
McDonnell Douglas MD-81 UHB –
General Electric GE36 and
PW-Allison 578-DX propfan engine testbed •
McDonnell Douglas F-15 STOL/MTD – Thrust vector,
flight control system testbed •
NASA AD-1 – Oblique Wing •
NASA Environmental Research Aircraft and Sensor Technology experimental aircraft – ALTUS, Pathfinder and Helios •
NASA Hyper III – Lifting body remotely piloted vehicle •
NASA M2-F1 – Lifting body/re-entry vehicle •
NASA Pathfinder – Solar-powered aircraft •
Northrop F-5 Shaped Sonic Boom Demonstrator – Shockwave reduction •
Northrop HL-10 – Lifting body/re-entry vehicle research •
Northrop M2-F2 – Lifting body/re-entry vehicle research •
Northrop M2-F3 – Lifting body/re-entry vehicle research •
Northrop N-1M – Flying wing research •
Northrop N-9M – Flying wing proof of concept aircraft for
Northrop YB-35 •
Northrop Tacit Blue – Stealth technology demonstrator •
Piasecki PV-2 – Helicopter technology demonstrator •
Piasecki VZ-8 Airgeep – Liftfan VTOL research •
Piasecki PA-97 1980 – Heavy lifter •
Republic XF-84H "Thunderscreech" – Supersonic propeller testbed •
Republic XF-91 Thunderceptor – Inversely tapered swept wing •
Rockwell HiMAT – Maneuverability and control research •
Rockwell XFV-12 – Augmented wing vectored thrust VTOL •
Rotary Rocket Roton 1999 – Single stage to orbit helicopter rocket •
Ryan VZ-3 Vertiplane 1958 – Blown flap VTOL research •
Ryan XV-5 Vertifan 1964 – Fan lift VTOL research •
Sawyer Skyjacker II – Low aspect ratio research aircraft •
Scaled Composites Proteus 1998 – Telecommunication relay testbed •
Schweizer SGS 1-29 1958 – Laminar flow research on wings made of metal •
Sikorsky S-69 1981 – Compound co-axial research •
Sikorsky S-72 1976 – Helicopter/aircraft hybrid research •
Sikorsky S-75 1984 – Advanced Composite Aircraft Program •
Sikorsky S-76 SHADOW 1985 – Sikorsky Helicopter Advanced Demonstrator and Operator Workload •
Stinson L-1 Vigilant – One example modified for boundary layer experiments •
Travel Air 2000 – One modified for Besler steam powered aircraft •
Vertol VZ-2 – tilt wing VTOL research •
Vought V-173 – Disk wing research for
Vought XF5U •
Vought V-326 – High-altitude test aircraft •
Vought-Sikorsky VS-300 – Helicopter ==See also==