Rubber cords in the apexes of the V-struts acted as shock absorbers. The first flight was made in late September 1928. Despite the lack of power it was able to carry three passengers and handled well. Without the passengers it could perform simple aerobatics. On the flight to the Second National Lightplane Contest in late October it suffered engine problems and had to make an emergency landing. Though it was not seriously damaged in the landing, its designers decided to convert the M.N.3 into a two-seater, designated the M.N.4. Partly because they were busy working on their final joint design, the Medwecki and Nowakowski M.N.5, and partly because of the closure of Samolot, the conversion was not completed until 1932. The main improvement was replacement of the Anzani engine by a Cirrus III upright four-cylinder, air-cooled inline. In addition, the front cockpit and the wing strut fairings were removed. These changes increased the empty weight by 34%. Its maximum speed was , it could climb to in 4 min 20 s and had a service ceiling of . After obtaining its certificate of airworthiness the sole N.M.4 was used by the P.W.S. flying club for about a year, then moved to the Gdansk club where it flew into the late 30s, participating in many meetings and regional and national competitions. In 1933 it competed in the Fifth National Lightplane Contest. Flown by Stefan Krynski, it came eleventh out of twenty-six.