The D. 520 was a French energy fighter designed to match the Bf 109 in combat, and to outmanoeuvre it if necessary. However, this advantage was outweighed by the underpowered engine that allowed such manoeuvrability and many aircraft using the same airframe were put into development to resolve this and several other issues in various ways. One of these projects was the D. 521, which simply sought to modify the plane to operate with similar agility with a stronger engine, namely the Rolls Royce Merlin II. However, the 1940 armistice, which ended the Battle of France with German victory, marked an end to all development on the D. 520 variations, at which point only one prototype of the D. 521 had been built and it was not even remotely ready for production, nor were its sister projects. As such, much about what would have become of the D. 521 had it not been discontinued is a mere "What if?"

Like my D. 520, the visual aspect of this aircraft was designed purely from memory, with references and research only being used for information on weight and engine power. As such, don't expect it to look or handle identically to the real thing, especially considering how shady what can be defined as "the real thing" is for this craft in particular. The engine, as briefly discussed in the D. 520 description, is 1000hp, as the Merlin II was 1030hp, compared to the 520's 840hp Hispano-Suiza engine. Since I used the D. 520 as a base, consider this an updated version of my first Dewoitine. Enjoy!