In World War I he served in the Austro-Hungarian Armed Forces, as a fighter pilot in the Imperial and Royal Aviation Troops.

[2] His victory string ran until 31 August, when he downed a Bristol F.2 Fighter, but lost all four of his inexperienced wingmen in the process.

[3] In 1918, Austria-Hungary dissolved and Navratil moved to the newly formed Kingdom of Serbs, Croats and Slovenes, where he took on a position in the royal army.

[1] With the establishment of the Independent State of Croatia on 10 April 1941 Navratil was brought back into active service.

After he was relieved of his post, reportedly due to complaints about the brutality of the government, he traveled to Vienna, where his family was located and remained there until the end of World War II.