The 24 CW-21Bs were assembled at Andir airfield, Bandung, Java, in February 1941, equipping Vliegtuiggroep IV, Afdeling 2 ("Air Group IV, No. 2 Squadron"; 2-VLG IV).
With its light construction, radial engine, low wing loading, limited pilot protection and lack of self-sealing fuel tanks, the CW-21B was the Allied fighter most similar to the opposing Japanese fighters.