A tail-sitter, or tailsitter, is a type of VTOL aircraft that takes off and lands on its tail, then tilts horizontally for forward flight.
Originating in the 1920s with the inventor Nikola Tesla, the first aircraft to adopt a tail-sitter configuration were developed by Nazi Germany during the Second World War. Development of such aircraft spiked during the late 1940s and 1950s, as aircraft designers and defence planners alike recognised the potential value of fixed-wing aircraft that could perform both a vertical take-off and vertical landing while also transitioning into and out of conventional flight. Inherent problems with tail-sitter aircraft were poor pilot visibility and control difficulties, especially during vertical descent and landing. Programmes to develop manned tail-sitters were typically terminated in the form of the more practical thrust vectoring approach, as used by aircraft such as the Hawker Siddeley Harrier and Yakovlev Yak-38.