WW-I flier, Leigh Brintnell formed Mackenzie Air Service in 1932. In 1935 MAS used a Bellanca 66-70 Aircruiser (called Eldorado Radium Silver Express - CF-AWR) to carry uranium ore concentrate from the Eldorado Gold Mine located on Great Bear Lake in the Northwest Territories to Edmonton Alberta for further shipment to Eldorado's refinery in Ontario. Two more Aircruisers were added to MacKenzie's fleet, CF-BKV in 1938 and CF-BTW in 1940. MAS also purchased a Noorduyn Mark-III Norseman (CF-AZA) to carry air mail.
While Brintnell was president of Northwest Industries in Edmonton, MacKenzie Air Service was amalgamated into Canadian Pacific Airlines in 1941.