In 1914, whilst still a senior student, he was offered his first job in Schwerin, where he worked in the construction of fighter aircraft for the German Fliegerkorps in the new Fokker-Flugzeugbau factory.
[1] With a biplane, which Fizir built in 1925, he won the first prize in the 1927 Little Entente contest, despite having an engine with only half the power of other competing designs.
[1] His greatest success was the Fizir FN two-seater with dual controls, over 100 of which were built, which was in use as a trainer up to 30 years after World War II.
Rudolf Fizir was awarded with the Paul Tissandier Diploma from the Fédération Aéronautique Internationale for achievements in aviation, and held the rank of pukovnik (colonel) in the Croatian Battle Air Force.
[1] After World War II, Fizir worked as a motorcycle designer, and continued with aircraft construction in his retirement years.