The Fokker D.XXI fighter aircraft was conceived in 1935 by the Dutch manufacturer Fokker, in response to the specifications established by the Royal Netherlands East Indies Army Air Force (ML-KNIL).
The D.XXI was intended to be a cost-effective, durable, and compact fighter that would deliver commendable performance for its time.
It entered service during the early phases of the Second World War, providing valuable support to both the Luchtvaartafdeling (Dutch Army Aviation Group) and the Finnish Air Force.
After the Netherlands was invaded and occupied in May 1940, several Dutch D.XXIs that were captured were later utilised by the Luftwaffe.
The Fokker D.XXI was initially deployed in combat by the Finnish Air Force during the Winter War of 1939–1940, which took place between the Soviet Union and Finland.
At the onset of the conflict, there were 41 aircraft in service with the Finnish forces, all equipped with the Mercury VIII engine.
On December 1, 1939, the D.XXI recorded its inaugural victory by downing a Soviet Tupolev SB.
The Fokker D.XXI was competitively matched against the Soviet Air Force’s aircraft, and its robust design, featuring a radial engine and fixed undercarriage, rendered it particularly effective in the challenging Finnish environment.
As the Winter War progressed and newer Soviet fighter models emerged, the Fokker D.XXI increasingly demonstrated its inadequacies in terms of power and armament, being equipped with merely four 7.92 mm/.312 in machine guns, which rendered it unable to compete effectively; proposals to enhance the Fokkers with 20 mm cannons were ultimately abandoned, with only one aircraft being fitted with two 20 mm cannons alongside two 7.92 mm/.312 in machine guns.
Additionally, another fighter featured retractable landing gear, but due to the less than expected enhancement in performance, this design was not carried forward in production.
The fixed undercarriage was advantageous for operations on unimproved runways and allowed for conversion to skis for winter conditions, both of which were beneficial in the Finnish operational environment.
Throughout the conflict, a total of 12 D.XXI aircraft were lost, with six of those losses attributed to accidents rather than enemy engagement.
The conflict between Finland and the Soviet Union was reignited during the Continuation War (1941–1944), with the D.XXI once again serving as a crucial component of the Finnish Air Force.
In the initial air engagement, six D.XXIs powered by Mercury engines successfully downed two Soviet Ilyushin DB-3 bombers.
Numerous pilots from the Finnish Air Force achieved the status of fighter aces flying the Fokker D.XXI.
Finland continued to utilise their D.XXIs until 1949, ultimately classifying them as surplus in 1952.
Despite the cancellation of the order by the ML-KNIL, the Luchtvaartafdeling proceeded to place an order for 36 aircraft, all of which were delivered in a timely manner to engage in the conflict against the Germans in May 1940.
On 10 May 1940, coinciding with the day Germany initiated its invasion of the Netherlands, 28 D.XXIs were operational and prepared for missions.
On that initial day, six D.XXIs provided escort for a group of Fokker T.V bombers targeting the Meuse bridges in an effort to impede the German advance; they encountered nine German Messerschmitt Bf 109s, and in the subsequent dogfight, one Bf 109 was downed and two others sustained damage, resulting in the loss of one D.XXI and two T.Vs.
On the same day, a squadron of D.XXIs successfully intercepted and shot down 37 out of 55 incoming Junkers Ju 52 transport aircraft that had crossed the border in the early morning.
Due to a significant number of aircraft becoming unserviceable from battle damage after the first day, a decision was made to regroup at Buiksloot, located north of Amsterdam, on 11 May.
Over the next four days, missions were conducted from Buiksloot by D.XXIs operating in both solo and small formations to escort allied units and engage in search-and-destroy operations.
On 11 May, at least two Bf 109s were documented as being shot down by D.XXI fighters.
Operations against the numerically superior German forces persisted until the middle of 14 May, when news of the Dutch capitulation reached Buiksloot.
Consequently, both the remaining aircraft and the airstrip were destroyed to prevent their capture by the Germans.
From the initial force of 28 D.XXI aircraft, only eight fighters remained operational.
Although the D.XXI was considerably slower and less heavily armed than the Bf 109, it exhibited surprisingly effective performance in combat due to its agility.
It was also among the few aircraft capable of following a Stuka bomber into its dive.
Nevertheless, the Luftwaffe’s numerical superiority resulted in the destruction of the majority of Luchtvaartafdeling D.XXI fighters throughout the campaign.
Some were captured during and after 15 May, but their subsequent fates remain unknown.
The LVA (Netherlands Air Force) achieved a total of 38 victories against the Luftwaffe during their confrontation with the German forces, with 16 of those victories credited to Fokker D.XXI pilots.
