First Lieutenant McDonnell was a crew member on a RB-29A with the 91st Strategic Reconnaissance Squadron, U.S. Air Force. On 13 June 1952, the aircraft departed Yokato Air Base, Honshu, Japan, on an electronic surveillance mission. It was shot down by 2 Russian MiG-15's over the Sea of Japan south of Mys Ostrovnoy, north of Hokkaido, and 120 miles from the Russian coast. He was listed as Missing in Action and was presumed dead on 15 November 1955.

For his leadership and valor, First Lieutenant McDonnell was awarded the Distinguished Flying Cross, 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.