In 1942, Gaiser was assigned to Jagdgeschwader 51 (JG 51—51st Fighter Wing) where he served as Rudolf Wagner's wingman.

Staffel of JG 51 which at the time was under the command of Oberleutnant Horst-Günther von Fassong.

[5] On 22 January 1944, Gaiser was last seen in combat with Ilyushin Il-2 ground-attack aircraft near Berdychiv, Ukraine.

All his air victories were achieved over the Eastern Front (World War II) and included 21 Il-2 Sturmoviks.

The Luftwaffe grid map (Jägermeldenetz) covered all of Europe, western Russia and North Africa and was composed of rectangles measuring 15 minutes of latitude by 30 minutes of longitude, an area of about 360 square miles (930 km2).