The Fokker D.XXI Onija ti a apẹrẹ ni 1935 fun lilo nipasẹ awọn Royal Netherlands East Indies Army Air Force (Militaire Luchtvaart van het Koninklijk Nederlands-Indisch Léger, milimita-KNIL). Bi iru, ti o ti a ṣe bi ohun ilamẹjọ ati kekere, sugbon gaungaun ofurufu, eyi ti o ní kasi išẹ fun awọn oniwe-akoko. Titẹ awọn operational lilo ni ibẹrẹ ọdun ti Ogun Agbaye II, o pese yeoman iṣẹ fun awọn mejeeji awọn Luchtvaartafdeling (Dutch Army Aviation Group) ati awọn Finnish Air Force, ati awọn kan diẹ won itumọ ti nipasẹ awọn El Carmolí factory ṣaaju ki o subu sinu ṣọtẹ ọwọ nigba ti Spanish Ogun Abele.