In the mid-1960s, Bristow opted to enter the North Sea market; being the second helicopter operator (after BEA Helicopters Limited) to establish operations at Aberdeen, Scotland, it was relatively well positioned to take advantage of the region's oil boom. Starting on 17 February 1965, the company operated the Westland Wessex 60 ten-seat helicopter to support these off-shore installations. Throughout the 1970s, Bristow would expand its Aberdeen operation, its main oil and gas support hub being based at Dyce Airport; in 1972, the company allocated the first of several Sikorsky S-61N to Sumburgh Airport in support of Shell's offshore rigs. Following an expansion programme, which included the building of new on-site accommodations for workers and their families, around thirty S-61N flights were routinely flying daily from Sumburgh, supported by round-the-clock maintenance coverage, at the peak of operations during the 1970s. During the 1980s, Bristow became Aberdeen Airport's largest single employer, its personnel in Aberdeen having increased a hundred-fold, as well as operating the majority of offshore flights in the North Sea. In 1980 alone, nearly 400,000 passengers and over 2,300 tons of freight passed through Bristow's Aberdeen terminal.