produced they had fixed undercarriages instead of the retractable undercarriage on later models. The original use for this aircraft was to keep Cook Strait services to Wellington operating while Rongotai airport was being rebuilt. The Herons operated mainly from Nelson in the South Island as well as to Blenheim, Rotorua, and Hamilton. Their heavy engines caused wing spar fatigue due to the light aluminium alloy used. Steel spars were substituted but with a weight penalty reducing passenger numbers to below economical levels. De Havilland did offer the Heron 2, a major improvement over the Heron 1 but this was not taken up. Heron ZK-BEQ was used as a royal aircraft when Queen Elizabeth II and Prince Philip visited New Zealand for the first time in 1953–54. When the old Rongotai airfield closed in 1957, the Herons were considered for the Nelson-Christchurch-Invercargill route but the aircraft were sold off to private operators instead. By then, only the DC-3 and Rapide/Dominies made up the NAC Fleet. The last type of piston engine airliner to be operated by NAC was a leased Mt Cook Airline Britten Norman BN2 Islander ZK-MCD, used during 1976–77 to operate a service on the Auckland – Whangarei – Kaitaia route. This was to allow services to operate while Kaitaia's compacted gravel runway was sealed for use by heavier aircraft. The Islander using an alternative grass strip. It was repainted in the "new" Wings of the Nation red and orange colour scheme. Turboprops Vickers Viscount 807 The pioneering turbo-prop powered Vickers Viscount first appeared in New Zealand in 1953 when an early model -700 was flown out for the London to Christchurch Air Race. In 1954, after the New Zealand Government encouraged the development of nationwide airports and with the promise of Wellington Airport being completed in 1958, NAC ordered four of the new larger 800 series type. The Vickers Viscount 807s were introduced from 1958, three initially being purchased. The first was used as a training aircraft and operated alone for a year on the Christchurch-Auckland route, and to Palmerston North which substituted for a still uncompleted Wellington International Airport. Services to Wellington began the following year, after the major reconstruction of Wellington's Rongotai Airport was completed a year later, two more Viscounts had joined the first by then. Services to Dunedin began late in 1962 with the purchase of the fourth aircraft in 1960, after the closure