In 1937, he applied for service in the Austrian Air Force but was rejected and joined the Army where he served with Infanterieregiment 3.

Following the Anschluss, the annexation of Austria into Nazi Germany on 12 March 1938, Fellerer applied for service in the Luftwaffe and was again rejected.

In April 1940, Fellerer was promoted to Leutnant (second lieutenant) and posted to the Kampffliegerschule-Ergänzungsgruppe, a supplementary training unit for bomber pilots.

[3] Following the 1939 aerial Battle of the Heligoland Bight, bombing missions by the Royal Air Force (RAF) shifted to the cover of darkness, initiating the Defence of the Reich campaign.

It consisted of a series of control sectors equipped with radars and searchlights and an associated night fighter.

Each sector, named a Himmelbett (canopy bed), would direct the night fighter into visual range with target bombers.

Gruppe (2nd group) of Nachtjagdgeschwader 1 (NJG 1—1st Night Fighter Wing) as Technical Officer.

On 16 June, his Messerschmitt Bf 110 D-0 "G9+DM" was hit by the defensive gunfire from the RAF Vickers Wellington W5447 from No.

Fellerer and his radio operator Oberfeldwebel Heinz Hätscher returned to Bergen airfield.

[Note 2] During the 1950s, he served with the Austrian Air Force, becoming Commander of the Langenlebarn Airbase in Tulln on the Danube, retiring as an Oberstleutnant.