Captain Costlow was a veteran of World War II. In Korea, he was a member of the 71st Ordnance Depot Company, 79th Ordinance Battalion. On 18 February 1952, he was piloting an observation aircraft which crashed near Ascom, South Korea, which killed him.

Costlow 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.