LTV XC-142 tiltwing experimental aircraft made by Ling-Temco-Vought. The LTV XC-142 was built in 1964 for the US army who were interested in a short take-off and landing aircraft that could carry huge cargo and travel long distances. Tiltwing aircraft have wings that can rotate vertically or horizontally. When rotated vertically, the engine propellers allow the aircraft to take off and land vertically much like a helicopter. Once in the air, the wings rotate to point horizontally and allow it to fly like a conventional airplane. It was able to transport heavy cargo but proved unstable at certain manoeuvres resulting in a cancellation of the project in 1966. NASA continued to test the plane until 1970.
#22 Is this one the only one still under testing?