Delivery of the first four D.21 fighters for the Dutch army air force. They are not armed yet. A month latre during the Munich Crisis the service could only form three small fighter flights, one with D.21s, one with D.XVIIs and one with C.10 reconaissance biplanes.

The D.21 or D.XXI was the closest thing to the Spitfire for three minor nations - Finland, Denmark, and Holland - in 1940, when Dutch military aircraft wore orange nationality markings. Serving with the White Mice squadron, the real 221 (c/n 5494), flown by Lt Herman Doppenberg, shot down a Bf 109 over Den Helder on 10 May 1940.