it was developing the VZ-9-AV Avrocar, a circular jet aircraft with an estimated speed of , German engineer Georg Klein claimed that such designs had been developed during the Nazi era. Klein identified two types of supposed German flying disks: A non-rotating disk developed at Breslau by V-2 rocket engineer Richard Miethe, which was captured by the Soviets, while Miethe fled to the US via France, and ended up working for Avro. A disk developed by Rudolf Schriever and Klaus Habermohl at Prague, which consisted of a ring of moving turbine blades around a fixed cockpit. Klein claimed that he had witnessed this craft's first crewed flight on 14 February 1945, when it managed to climb to in 3 minutes and attained a speed of in level flight. Miethe claimed he had worked on the V-2 program but no corroborating evidence exists. Georg Klein claimed the engineer had escaped capture by the Soviets in Breslau by flying out in a Messerschmitt Me 163 Komet, which would have been impossible. There is no evidence that Habermohl even existed. Rudolf Schriever claimed he had worked for Heinkel as a test pilot and engineer between 1940 and 1941, but this has never been corroborated. In post-war Germany, Schriever drove supply trucks for the US Army but told newspaper reporters that delegates from foreign powers were constantly making him offers regarding his wartime projects. Aeronautical engineer Roy Fedden remarked that the only craft that could approach the capabilities attributed to flying saucers were those being designed by the Germans towards the end of the war. Fedden (who was also chief of the technical mission to Germany for the Ministry of Aircraft Production) stated in 1945: Fedden also added that the Germans were working on a number of very unusual aeronautical projects, though he did not elaborate upon his statement. Nazi UFO conspiracy theories By the 1960s, fringe authors began spreading tales of Nazi UFOs that were tied to the occult or aliens. According to these theories and fictional stories, various potential code-names or sub-classifications of Nazi UFO craft such as Rundflugzeug, Feuerball, Diskus, Haunebu, Hauneburg-Gerät, Glocke, V7, Vril, Kugelblitz (not related to the self-propelled anti-aircraft gun of the same name), Andromeda-Gerät, Flugkreisel, Kugelwaffe, Jenseitsflugmaschine, and Reichsflugscheibe have all been referenced. Model kit companies like Airfix and Revell have released kits of the "Haunebu", and it is featured in video games like X-Plane 11 and