sentences:  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.