[2] In 1933, work began on a derivative of the D.332 with a retractable undercarriage, the D.335, to meet the requirements of Air France and the Belgian airline SABENA, but the crash of the D.332 resulted in a redesign of the aircraft's structure being needed.

[3] Dewoitine could not meet the tight timescales required by SABENA, however, and the Belgian airline cancelled its order on 15 March 1935.

The aircraft were powered by three 650 hp (480 kW) Hispano-Suiza 9V16/17 radial engines (license-built versions of the American Wright R-1820 Cyclone) driving constant-speed propellers.

[5][12] On confirmation of the D.338s satisfactory performance, a series of orders were placed by Air France and the French government, with 31 D.338s built in total.

[5] The Dewoitine D.620 was designed to meet a 1933 French government requirement for an airliner to carry 30 passengers, and was powered by three Gnome-Rhône 14K radial engines rated at 865 hp (645 kW).

[13][14] In 1936, Emile Dewoitine proposed the production of a more advanced derivative of the D.620 with an elliptical section monocoque fuselage and more powerful engines.

The proposal was accepted by the French government, and in 1937, after Dewoitine had resigned from his company which had been nationalised as part of SNCAM, the new type was designated D.342.

[18][19] The prototype D.338 received its certificate of airworthiness on 26 June 1936,[20] and entered into service with Air France on the Paris–Lyon–Marseille route on 13 July 1936.

[26] Following the Armistice of 22 June 1940, the Vichy French government set up a civil liaison service, which continued to operate the D.338.