Risør and Arendal. Other activities involved crop dusting of forest for Felleskjøpet. The airline also provided a target service for the military. Four aircraft were permanently used to tow a target about behind the aircraft, and military personnel would practice shooting at the target. During the 1960s, Vestfoldfly never received a concession for a regular, scheduled flight from Sandefjord to Oslo. The reason was that the Skien-based Fjellfly held the concession for the routes from Oslo to Sandefjord, Tønsberg and Skien. Fjellfly never used its landing rights at Sandefjord, but nevertheless still hindered Vestfoldfly from starting a competing route. Skaunfelt eventually split his activity in two, demerging the aviation school and renaming it Den Norske Luftfartsskole, which remained in operation until 1999. The other activity was renamed Norsk Flytjeneste. In 1969, Norsk Flytjeneste and Jotun, a large Sandefjord-based industrial company, established Penguin Air Service, where Norsk Flytjeneste owned 25 percent of the shares. Penguin Air Service company bought a six-seat Piper PA-31 Navajo and started charter services for Jotun. In 1975, Bugge Supplyship also joined the joint venture and a second aircraft was bought. Most of the traffic was for the oil industry to Stavanger. Norsk Flytjeneste In 1972, Norsk Flytjeneste purchased two 50-passenger Douglas DC-6Bs from Braathens SAFE and leased one from Sterling Airways. They were used for domestic and international charter. The largest contract was from the Norwegian Church Aid, who contracted Norsk Flytjeneste to fly aid to Bangladesh. However, the airline failed to make money on the DC-6s, mostly because of the high operating costs, and sold them after a year. The company followed up with purchasing a ten-seat Cessna Citation business jet that they offered in the charter market. However, the market was not large enough, and the jet was sold. The main market for the charter services was Stavanger Airport, Sola, mainly serving transport of personnel in the oil industry. By the 1980s, Norsk Air had up to four daily round trips between the two cities. In 1983, the airline received concession to start a regular scheduled service to Stavanger. A ten-seat Beechcraft Super King Air was bought and services started on 12 January 1984. Services to Bergen Airport, Flesland started on 10 July. Soon there were four daily round trips to both cities, supplemented by charter trips operated by Penguin. Starting on 26 March 1984, Norsk Flytjeneste experienced competition on the routes from Sandefjord