Unique Flying Machines Sikorsky S-72: This March, we're celebrating the Sikorsky S-72 - an experimental aircraft developed in the mid-1970s.Once modified with an X-wing, this unique aircraft was designed for vertical takeoffs just like a helicopter.The rotary X-shaped wing could also be stopped in mid-flight to provide additional lift.Though development and testing of the modified S-72 X-wing were approved in 1983 and a prototype was unveiled in 1986, the program was canceled in 1988 before the aircraft ever flew.
