The Avro Canada VZ-9 Avrocar is a VTOL aircraft which resembles a flying saucer, developed as part of a secret U.S. military project from 1958 to 1961

The specifications section is hilarious. They were a tad optimistic...

Estimated maximum speed: 480km/h (300mph) Actual maximum speed: 56km/h (35mph)

Estimated range: 1,601km (995mi) Actual range: 127km (79mi)

Estimated service ceiling: 3,000m (10,000ft) Actual service ceiling: 0.91m (3ft)