The Fokker D.XXI was an inexpensive, simple and rugged design that was slower and more lightly armed than the opposing Messerschmitt Bf109 but was more manoeuverable. It could perform well against those aircraft but was overwhelmed by superior numbers.

It was designed in 1935 for the Royal Netherlands East Indies Army Air Force but a change in defence policy by the Dutch after the first flight of the prototype resulted in no orders being placed.

The Finnish Air Force had meanwhile expressed interest in the aircraft and placed orders for 7 and obtained a manufacturing license for the type, eventually building 93 aircraft.

Foreign interest and orders resulted in the Dutch reassessing the aircraft and orders were placed for 36 examples.

The last of these was delivered on 8 September 1939. These aircraft participated in defence actions against the Germans in May 1940 and flew numerous sorties from 10 May to the capitulation on 14 May.

One restored aircraft has been made from three airframes in Finland and there are two replicas in Holland.

Black Sea Toys (Frog) 1/72 kit completed by Steve Pulbrook in 2018.