Previously-secret USAF documents, released in 1995 under the US Freedom of Information Act showed that Avro Canada was developing two flying saucer designs in 1954. Code-named Silver Bug, one of the projects had a requirement for a maximum speed of Mach 3.5 and service ceiling in excess of 80,000ft. This rather unlikely scenario shows a Silver Bug slicing through a Tu-95 Bear. The flying disc would have had hardened leading edges and the attack would be at high sub-sonic speed.
Several variants of the WS-606A were studied by Avro Canada, including this finless, four-engine layout. The WS-606A was planned to be supersonic, have a vertical take-off and landing capability, and could have been configured as an interceptor or light bomber. Of interest to the RCAF and USAF, some of the funding was provided from the Pentagon's 'black' budget. After hundreds of hours of wind tunnel testing the project was eventually cancelled in 1960.