From the improvised airfield near Prijedor he carried out a number of sorties against Axis forces, the most notable being the attack on an Ustaša column near Orahovo on 4 June.

[citation needed] On 14 October Kluz became the station commander of the First Air Base of the Yugoslav National Liberation Army (YNLA) in Livno.

After the German offensive, Kluz was sent, with 200 men, to Allied-controlled Italy, where they received training, equipment and aircraft from the RAF.

[citation needed] Kluz became a member of the 1st Air Squadron of YNLA (Prva eskadrila, NOVJ), otherwise known as No.

For his wartime service, Franjo Kluz was posthumously awarded the Order of a People's Hero of Yugoslavia.