The Aero A.42 was a Czechoslovakian bomber aircraft of 1929 that was only ever produced in prototype form. For its day, it was an advanced design, with a sleek monoplane configuration. However, the Czech Air Force was not satisfied with it for a number of reasons, in particular, the aircraft's take-off and landing rolls were felt to be excessively long, and crew complained about the cramped cabin. The air force suggested a set of modifications to Aero, including replacing the wooden wing with a metal one, but Aero discontinued development.