Castoldi based the design of the M.67, (a single-seat, low-wing, monoplane, twin-float floatplane), on that of the earlier Macchi M.39, which had competed for Italy in the 1926 and 1927 Schneider Trophy races, following the M.39's layout but strengthened to accommodate the 18-cylinder, 57.256 L (3,494 cu in), 1,341 kW (1,798 hp) Isotta-Fraschini Asso 1000("Ace") 1000 W-18 engine, a much bigger and more powerful engine than the Fiat AS.2 V12 fitted to the M.39.

The M.67 carried fuel in its floats; the powerful engine drove a three-bladed propeller which created a large amount of torque.

[2] The race took place at Calshot Spit in the United Kingdom and began on 7 September 1929, with Lieutenants Remo Cadringher and Giovanni Monti flying the two M.67s.

Cadringher's M.67 began the race with an impressive burst of speed, but skidded in the first turn as its cockpit filled with blinding, choking smoke, and fumes; Cadringher went into a high-speed spin, pulled out of it over land, then completed one lap at an average speed of 457 kilometers (284 mi) per hour before having to land, unable to see the pylons marking the turns due to smoke in the cockpit.

Tomorrow our work as competitors will begin,"[3] signalling Italy's intention to be more competitive in the next Schneider Trophy race, scheduled for 1931.