The prototype, designated the IK-L1, of the design was ordered from Ikarus A.D. in 1934, and was delivered for test in 1935. The aircraft was powered by a Hispano-Suiza 12Ycrs inline engine. The forward-firing armament consisted of a 20 mm HS-404 cannon mounted under the engine, and two 7.92 mm Darne machine guns, mounted under and to each side of the engine. The design was similar to the Polish PZL P.8, sharing its Pulawski wing (gull-wing) design, giving the pilot an excellent view. The wing on each side was braced with two struts; the fixed conventional landing gear was spatted and mounted off the wing struts. The fixed tailwheel was also spatted. The pilot was installed aft of the wing in an enclosed cockpit. The horizontal stabilizer on each side was braced from below with two rigid braces from the lower tailcone, and tied from above with two flying wires from the vertical stabilizer. The three-bladed propeller was manually adjustable in pitch.
Captain Leonid Bajdak, a biplane advocate, tested the IK-1 in flight. During a full range of tests on the third flight the aircraft failed to pull out of a power dive and crashed. Bajdak bailed out and survived but claimed the IK-1 was not suitable as a fighter. Investigation of the wreckage disclosed that the failure was due to negligence in sewing a seam on one of the fabric-covered wings, and therefore a decision was made to proceed with the second prototype, designated IK-2. The second prototype had metal-skinned wings and a shallower cooling radiator. The IK-2 was ready for test in June 1936. A new test pilot, Dobnikar, performed the preliminary flight tests, including a mock battle against a Hawker Fury biplane fighter, flown by Captain Bajdak. The IK-2 outperformed the biplane in all respects, thereby confirming the hopes of the young designers.