Captain McWhirk was the pilot of a F-84E Thunderjet fighter with the 522nd Fighter-Escort Squadron, 27th Fighter-Escort Wing. On 2 January 1951, while on a combat mission of placing napalm on an enemy gun emplacement near Tongdung-ni, Korea, his aircraft crashed. He was listed as Missing in Action and was presumed dead on 31 December 1953. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

McWhirk was awarded the Air Medal with Oak Leaf Cluster, the Commendation Ribbon, the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.