The Fokker D-XXI fighter - may 1940
The Fokker D-XXI (1936) was a surprisingly effective dogfighter for low and medium altitude air-combat, with a remarkable steep-turn capacity. Yet, successful as it was as a dogfighter, it lacked sufficient speed and acceleration for an interception role.
Equipped with four wing-mounted 7.9 mm rapid fire FN machine guns it was only modestly armed. Its maximum speed was 460 km/hr, making it (already four years after its introduction) an under-powered fighter for the 1940-skies. In May 1940, with the Luftwaffe packed skies, it was, nevertheless, a quite effective fighter. It was usually flown by capable pilots, that managed to maintain a positive air-combat score-card against adverseries like the Bf-109 and Bf-110.
The D-XXI proved also very successfull when it was used by the Finnish airforce, that scored hundreds of kills with these planes against the largely obsolete Sovjet airforce of those days (1939).
Some D-XXI pilots would later make successful Spitfire pilots in the RAF. The most famous of those was - without a doubt - Bram (Bob) van der Stok, who would eventually become squadron leader of 322 RAF (Dutch) squadron, but who would become more celebrated for his escape from Stalag Luft III (the Great Escape), that he and two Norvegian officers were the only three successful escapees of.