The Aero A.34 Kos (Czech: "Blackbird") was a small sports and touring biplane built in Czechoslovakia in the 1930s.

Of conventional biplane configuration and wooden construction, it featured wings that could be folded to allow it to be towed to and from airfields by automobile (width 2.91 m).

A prototype (registration L-BASO) had an 85 hp Walter Vega radial engine.

It took part in the Challenge 1929 international contest (piloted by Josef Novak), but had to withdraw due to engine failure and crash-landing on August 8, 1929.

They were used as trainers and sports planes in Czechoslovak civilian and military aviation.