Restore the side frame if it‘s missing!

Designation Official, Popular Name(s) Manufacturer 1st Flight or Appearance Role(s)/Notes

X-1         Skyrocket             Bell        1948    experimental 1st supersonic aircraft - redes.

X-2         Transonic             Bell        1948    experimental supersonic rocket - 1st aircraft
                                                      to fly > Mach 3 - redes. S-2

X-3         Stiletto              Douglas     1948    experimental supersonic research
                                                      aircraft- redes. S-3

X-4         Bantam                Northrop    1948    experimental high-speed tailless research
                                                      aircraft- redes. S-4

X-5         Variable-Sweep        Bell        1948    experimental - 1st American swing-wing jet -
                                                      redes. S-5

X-6         Crusader,             Convair     1955    nuclear propulsion testbed - 1 modified [N]B-36H
            Peacemaker, Aluminum Overcast, Magnesium Overcast

X-7         The Flying Stovepipe  Lockheed    1951    super/hypersonic ramjet testbed - "pilotless

X-8         Aerobee               Aerojet     1947    high-altitude research missile

X-9         Shrike                Bell        1950?   simplified version of the GAM-63 ASM

X-10                              North Amer. 1955    testbed SM-64 Navaho missile

X-11        Atlas A               Convair     1957    ballistic missile evaluation B-65

X-12        Atlas B/C/D           Convair     1958    testbed B-65/SM-65 Atlas

X-13        Vertijet              Ryan        1955    experimental jet VATOL

X-14                              Bell        1956    experimental VTOL - 2 jets in nose

X-15        Hypersonic            North Amer. 1959    manned rocket - flew > 4000 mph & higher than
                                                      500,000 feet

X-16                              Bell        1955    experimental - competitor U-2 -cancelled

X-17                              Lockheed    1956    experimental rocket

X-18        Tilt Wing             Hiller      1959    experimental tilt-wing convertiplane -
                                                      modified C-122

X-19        Tilt Prop             Cur.-Wr.    1963    experimental 4 tilt-prop VTOL

X-20        Dyna-Soar, Dinosaur   Boeing      1965    experimental hypersonic lifting body

X-21        Laminar Flow          Northrop    1963    experimental modified Douglas WB-66 -laminar flow
                                                      research with 3.2 million slots & 815,000
                                                      holes on wing

X-22        Tilt Duct             Bell        1965    experimental 4-engined swiveling engined VTOL

X-23        Prime                 Martin      1966    experimental hypersonic lifting body

X-24A       Flying Potato         Martin      1969    experimental lifting body

X-24B       Flying Flatiron       Martin      1973    X-24B - modified, more angular X-24A

X-25        Gyro-glider, DDV      Bensen      1978    experimental rescue mini-helicopter

X-26A        Frigate              Schweizer   1972?   exper. USN sailplane civ. SGS 2-32

X-26B       Q-Star                Lockheed    1968    modified QT-2 - exper. trainer

X-27        Lancer                Lockheed    1971    exper. - proposed modified F-104

X-28        AirSkimmer, Osprey I  Pereira     1970    exper. light patrol flying boat

X-29        Polecat               Grumman     1984    experimental FSW demonstrator

X-30        NASP                  Rockwell    1989    experimental hypersonic low-orbit transport

X-31        EFM                   Rock./MBB   1987    experimental highly maneuverable fighter

X-32                              Boeing      1996    full-scale tech. demon. (FSTD) of JSF (Joint
                                                      Strike Fighter) - competitor of X-35

X-33                              Lockheed    1996    demonstrator of SSTO (Single Stage To Orbit) RLV
                                  Martin              (Reuseable Launch Vehicle) - lifting body configuration

X-34                              Orbital     1995?   NASA test vehicle for unmanned reusable
                                  Sciences            space launcher

X-35                              Lockheed    1996    FSTD of JSF  - competitor of X-32

X-36                              NASA/McDD   1996    stealthy, highly maneuverable 27% scale drone of
                                                      proposed manned fighter - tailless, cranked-arrow wing

X-37        Future-X              Boeing      1998    proposed exper. flight vehicle - test
                                                      earth-to-orbit and orbit-to-orbit reusable
                                                      space trans. technologies

X-38        Lifeboat              Scaled Comp.1996    experimental CRV (Crew Return Vehicle) - lifting body

X-39                                          2000?   presently unassigned; reserved for USAF Research Lab.,
                                                      originally used for unmanned subscale demon. for
                                                      Future Aircraft Technology Enhancements (FATE) to fighters,
                                                      but funding transferred to DARPA

X-40                              Boeing      1998    USAF SMV (Space Maneuver Vehicle) program - used
                                                      for drop tests evaluating "autonomous approach and
                                                      landing systems" from H-60; B-52 drops planned

X-41                                                  USAF - classified, but supposedly "an exper. maneuverable
                                                      reentry vehicle carrying...payloads through a suborbital
                                                      trajectory, and reentering and dispersing the payload
                                                      in the atmosphere"

X-42                                                  classified - "exper. expendable liquid rocket motor
                                                      upper stage designed to boost 2000-4000 lb. payloads
                                                      into orbit

X-43        Hyper-X                                   several Mach 7-10 scramjet-powered test vehicles
                                                      boosted to test speed and altitude by Pegasus boosters
                                                      launched by B-52s - evalation of SSTO tech.
X-44        Manta                             2000    designation reserved for possible NASA
                                                      full-scale manned tailless flight control demonstrator

X-44                              Lockheed    200?    Highly modified F-22A by removing tail, installing
                                                      delta wings, pitch/yaw low observable nozzles,
                                                      pneumatic vortex control, and mechanical
                                                      and fluidic thrust vectoring nozzles;
                                                      designation in conflict with X-44 Manta

X-45                              Boeing      2000    UCAV demonstrator

X-46                              Boeing      2001    "low-cost approach" to USN's planned naval unmanned
                                                      combat air vehicle (UCAV-N) technology demonstration - F/A-18 to be
                                                      used as "manned surrogate"

X-47        Pegasus               Northrop    2001    demonstration UCAV (Unmanned Combat Aerial Vehicle)
                                  Grumman Integrated  under development for US Navy/DARPA
                                  Systems Sector 
X-48                              Boeing/    2001     blended-wing body slow-speed flying wing demonstrator

X-49?                                                 possibly skipped at Boeing's request for X-50?

X-50        Dragonfly             DARPA/      200?    CRW (canard rotor/wing) exper. unmanned demonstration vehicle;
                                  Boeing              rotor converts to fixed wing

XS                                Cox-Klemin  1927    USN/USMC scout flying boat biplane
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