Having completed the program in July 1931, Suprun was assigned to the 91st Fighter Aviation Squadron as a flight commander.

He met Aleksandr Pokryshkin (who later became a flying ace and thrice Hero of the Soviet Union) during a vacation on the coast of the Black Sea in 1935.

His unit of roughly 50 aircraft was assigned to the city of Chongqing until they were transferred to Yunnan in December where they were tasked with protecting strategically important airfields and equipment.

[6] Two days after the start of Operation Barbarosa, Suprun requested permission from the institute to create and command a regiment composed of test pilots.

Despite being a regimental commander, he flew combat sorties, and he scored his first aerial victory on 27 June 1941, a Hs 126.

[6] He was killed in action on 4 July 1941 after engaging a Luftwaffe plane; it is unclear if he scored an aerial victory during his last dogfight and some sources indicate he shot down a Bf-109 right before his death.

[7][8] After his death he was awarded the gold star a second time, making him the first person to become a twice Hero of the Soviet Union during the war.