On 8 January 1959, the first Argosy performed its maiden flight. It appeared during that year's Farnborough Airshow, by which point five aircraft were flying, having cumulatively amassed about 400 flight hours between them. Certification-related testing of the type was reportedly completed during September 1960. In December 1960, the Argosy received type certification from the American Federal Aviation Administration (FAA), authorising the aircraft's entry to commercial service. 10 of the initial civil version, the Series 100, were built; construction of these aircraft had commenced months prior to receiving certification so that deliveries could commence as soon as possible.