conventional propeller, and in the transition from vertical to forward flight the lift would have transferred to the wing. Cold War era During the 1950s, aircraft designers around the world engaged in programmes to develop fixed-wing aircraft that could not only perform both a vertical take-off and vertical landing, but transition into and out of conventional flight as well. As observed by the aviation author Francis K. Mason, a combat aircraft that possessed such qualities would have effectively eliminate the traditional reliance on relatively vulnerable runways by taking off and landing vertically as opposed to the conventional horizontal approach. Accordingly, the development of viable vertical take-off and landing (VTOL) aircraft was particularly attractive to military planners of the early postwar era. As the thrust-to-weight ratio of turbojet engines increased sufficiently for a single engine be able to lift an aircraft, designers began to investigate ways of maintaining stability while an aircraft was flying in the VTOL stage of flight. One company that opted to engage in VTOL research was the French engine manufacturer SNECMA who, beginning in 1956, built a series of wingless test rigs called the Atar Volant. Only the first of these was unpiloted and the second flew freely, both stabilized by gas jets on outrigger pipes The third had a tilting seat to allow the pilot to sit upright when the fuselage was level and had the lateral air intakes planned for the free flying aircraft, though it always operated attached to a movable cradle. The pilot for these experiments was Auguste Morel. However, the Atar Volant was not an end onto itself; its long term purpose was to serve as precursors to a larger fixed-wing aircraft. Independently of this work, substantial influence on the direction of development came from the Austrian design engineer Helmut von Zborowski, who had designed an innovative doughnut-shaped annular wing that could function "as power plant, airframe of a flying wing aircraft and drag-reducing housing". It was theorised that such a wing could function as a ramjet engine and propel an aircraft at supersonic speeds, suitable for an interceptor aircraft. SNECMA's design team decided to integrate this radical annual wing design into their VTOL efforts. Accordingly, from this decision emerged the basic configuration of the C.450 Coléoptère. In December 1958, the Coléoptère first left the ground under its own power, albeit while attached to a gantry. Several challenging flight characteristics were observed,