A gifted pilot, Brumowski was the Austro-Hungarian Empire's highest scoring ace. When war was declared, he was serving as an officer in an artillery regiment. After distinguishing himself in combat on the Russian front, he transferred to the air service in July 1915. Posted to Flik 1, he frequently flew missions as Otto Jindra's observer before becoming a pilot on 3 July 1916. In November 1916, Brumowski joined Flik 12 on the Italian front. Scoring five victories in less than two months, he was one of the few Austro-Hungarian pilots to receive the Gold Medal for Bravery. In March 1917, after studying German fighter tactics with Jasta 24 on the Western Front, he assumed command of Flik 41J, the first true Austro-Hungarian fighter squadron. Though he continued to favor the Hansa-Brandenburg D.I, Brumowski began flying the Albatros D.III in the summer of 1917, scoring his first victory with this aircraft on 17 August. By October 1917, his Albatros had been painted red, and when airborne, his squadron was easily identified by the macabre insignia Brumowski designed: a white skull on a black background. Having been recognized as an extraordinary leader, he was given command of all Austro-Hungarian fighter squadrons of the Isonzo on 11 October 1918.
After the war, Brumowski tried his hand at farming on his mother-in-law's estate in Transylvania. When that venture failed, he moved to Vienna where he operated a flying school until he was fatally injured in a plane crash in 1936 at the Schiphol airport near Amsterdam.