The Avia B.135 was a cantilever monoplane fighter aircraft from Czechoslovakia.
It represented the production variant of the Avia B.35, which was developed shortly prior to the war, and was based on the B.35/3 prototype (which included a retractable main undercarriage) but incorporated a newly designed all-metal wing.
The B.135/1 prototype garnered the interest of officers from the Bulgarian Air Force who were visiting the Avia plant, leading to the signing of a production contract for 12 aircraft and 62 engines, along with a license permitting the construction of an additional 50 airframes by DAR, designated as the DAR 11 Lyastovitsa.
Nevertheless, the DAR facilities were found to be inadequate for the production of the aircraft, resulting in only the 12 examples built in Czech.
The RLM halted plans for further production and also ceased engine deliveries after 35 units, subsequently encouraging the Bulgarian Air Force to acquire the Messerschmitt Bf 109 instead.
During their operational period, the B.135s experienced persistent engine issues, leading to their eventual assignment to training duties.
Nevertheless, four of these aircraft engaged in combat on 30 March 1944, successfully intercepting USAAF bomber formations that were intruding into Bulgarian airspace following their assault on Ploieşti; in this confrontation, one B-24 Liberator was downed.
