"The VZ-9- AV Avrocar was a Canadian VTOL aircraft developed by Avro Aircraft as part of a secret US military project carried out in the early years of the Cold War. Two prototypes were built as "proof-of-concept" test vehicles for more advanced USAF fighter and US Army tactical combat aircraft. The Avrocar intended to exploit the Coandă effect to provide lift and thrust from a single "turborotor." Thrust from the rotor was diverted out the rim of the disk-shaped aircraft to provide anticipated VTOL-like performance. In the air, it would have resembled a flying saucer. In flight testing, the Avrocar proved to have unresolved thrust and stability problems that limited it to a degraded, low-performance flight envelope; subsequently, the project was cancelled in 1961"

quote from youtube

video found at wired
http://www.wired.com/dangerroom/2010/12/real-life-ufos/?pid=157