Numerous early airlines adopted the Envoy for their fleets. The British company North Eastern Airways was the first to use the type as an airliner; multiple Envoys were used by the firm, which encountered difficulties on some routes due to limited passenger demand and navigation difficulties, leading to its discontinuation in 1938. The Indian operator Tata Air Service operated a single Envoy on a demonstration flight between Bombay (known as "Mumbai" today) and Calcutta (since re-spelt as "Kolkata") on 25 February 1935 to validate the viability of air mail service between the two cities. Amongst the more successful airlines to operate the Envoy was Japan Air Transport Co. (NKYKK – Nihon Koku Yuso KK) and the Czechoslovakian firm Czech Airlines (CSA), the latter having ordered four Envoys to launch its operations with on 1 October 1935.