USMA Class of 1950, First Lieutenant Flinn was a veteran of World War II, serving as an enlisted man. In Korea, he was a member of the 65th Engineer Combat Battalion, 25th Infantry Division. He was severely injured south of Chorwon, Korea, and evacuated to Japan, where he died on 9 October 1951.

Flinn was awarded the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation, the Republic of Korea War Service Medal and the World War II Victory Medal.