Northern Mountain began operations at Fort St. James in 1959 and by 1971 was one of the larger airlines in British Columbia. With a mixed fleet of Cessnas, de Havilland Beavers, Beechcraft Model 18s, Grumman Goose, and helicopters; Northern Mountain had spread its wings over most of the North including Alberta, Yukon and Northwest Territories. By spinning off its airplane division to merge with Thunderbird in 1971, Northern Mountain was able to concentrate its efforts on helicopters only and did so through 2000.

Thunderbird started in the early 1960s when it acquired the bush operations of Pacific Western Airlines in Prince George. From its base at Tabor Lake, Thunderbird operated Cessnas, Beavers and Otters on floats and skis servicing the new town of Mackenzie and the northern villages and logging camps of Williston Lake. In the early 1970s, Thunderbird secured a subcontract from Pacific Western Airlines to service the smaller communities of B.C. to feed that traffic into PWA's jet aircraft at Prince George, Kamloops and Kelowna. The need for a hangar on the Prince George Airport to fulfill this contract was the catalyst for the merger talks that resulted in the formation of Northern Thunderbird Air in 1971.

In the 1980s, the company had 18 aircraft, 3 bases, 21 scheduled points and numerous employees, but by the lare 1990s, the company had shrunk to 1 aircraft, 1 base, 2 scheduled points and 5 employees. NT Air has grown again to 10 aircraft, 3 bases, 7 scheduled points and 50 employees.

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