The Curtiss-Wright CW-21B was the primary combat variant of the lightweight interceptor series. The most significant improvement over the earlier CW-21A was the redesigned landing gear, which retracted inwardly into the wing rather than rearward into fairings. In 1940, 24 units were delivered to the Militaire Luchtvaart van het Koninklijk Nederlands-Indisch Leger (ML-KNIL) in the Dutch East Indies. Despite lacking armor and self-sealing fuel tanks, the CW-21B’s superior climb rate allowed it to engage Japanese bombers and fighters effectively during the early stages of the Pacific War before being overwhelmed by superior numbers