The Aero A.42 was a Czechoslovak single-engine land-based bomber prototype developed by Aero (now known as AERO Vodochody AEROSPACE a.s.). First flown in 1929, the aircraft represented a significant shift in design philosophy for the manufacturer, moving away from traditional biplane configurations toward a more modern high-wing cantilever monoplane design with fixed landing gear. Only two examples of the A.42 were ever built, and the aircraft never entered series production.
Designed for a crew of three—consisting of a pilot, an observer/bombardier, and a radio-operator/gunner—the A.42 was considered an advanced design for its era. Its technical capabilities were highlighted on September 20, 1930, when one of the prototypes established international speed records over a 1,000 km closed circuit. During these trials, the aircraft achieved a speed of 253.42 km/h (157.47 mph) while transporting payloads of 500 kg and 1,000 kg, proving its efficiency in high-payload transport.
Power was provided by a single Isotta Fraschini Asso 750, an Italian-made W-18 water-cooled piston engine capable of producing between 600 and 750 kW (800–1,000 hp). This powerplant enabled a maximum speed of 270 km/h and a cruise speed of 250 km/h. The aircraft had a service ceiling of 7,000 m and could climb to 5,000 m in 50 minutes. Its armament consisted of two 7.9 mm machine guns—one located in a dorsal turret and one in a ventral position—along with a standard bomb load of 200 kg of small bombs.
In terms of service, the A.42 was used exclusively for experimental and evaluation purposes. One prototype was operated by the Czechoslovak Air Force until 1938. Following the division of Czechoslovakia, this aircraft was transferred to the Slovak Air Force and was likely scrapped by 1940. Because it remained a prototype, the A.42 saw no combat service. Today, the aircraft is remembered as a technical milestone for Aero, a company that has evolved from producing early bombers to becoming the largest aircraft manufacturer in the Czech Republic, famous for its L-29 Delfín and L-39 Albatros jet trainers.