In 1953, the proposed airliner received the name "Friendship". A total of four prototypes were produced, two of these being flyable aircraft that were used for the test flight programme and were paid for by the Netherlands Institute of Aircraft Development; the other two prototypes were for static and fatigue testing. On 24 November 1955, the first prototype, registered "PH-NIV", performed its maiden flight. The second prototype and initial production machines were 0.9 m (3 ft) longer than the first prototype in order to address a revealed tendency for slightly tail-heavy handling as well as to provide additional space for four more passengers, raising the maximum number of passengers which could be carried to 32. These aircraft were also powered by the Dart Mk 528 engine, which was capable of generating greater thrust.