The Morane-Saulnier M.S. 278 was the designation given to the second M.S. 225 after it was fitted with a diesel engine. The M.S. 225 was a parasol wing fighter that was ordered into limited production in the early 1930s in order to fill a gap before the arrival of more modern fighters. The M.S. 278 was produced by installed a 520hp Clerget 14Fos diesel engine in the second M.S. 225. The conversion was not a success, and only the single aircraft was converted.