Nial Castle was born on September 27, 1920, in Cananea, Mexico. He enlisted in the U.S. Army Air Corps on May 28, 1941, and was trained as an aerial gunner, serving with the 91st Observation Squadron before entering the Aviation Cadet Program of the U.S. Army Air Forces on May 24, 1942. He was commissioned a 2d Lt and awarded his pilot wings at Spence Field, Georgia, on February 16, 1943, and then served as a flying instructor from February to December 1943. Lt Castle next completed P-38 Lightning transition training and joined the 8th Fighter Squadron of the 49th Fighter Group in New Guinea in January 1944. He was credited with the destruction of 5 enemy aircraft in aerial combat before joining the 93rd Air Service Squadron in the Philippines in May 1945. At the end of the war he deployed with the squadron to Okinawa and then on occupation duty in Japan before leaving active duty and Joining the Air Force Reserve on April 5, 1947. Capt Castle was recalled to active duty in the Air Force on March 1, 1951, and served as a C-119 Flying Boxcar pilot in Japan and Korea until leaving active duty on October 28, 1953. Maj Castle remained in the Air Force Reserve until his retirement on November 1, 1960. Nial Castle died on August 1, 2011.

His 1st (of 3) Distinguished Flying Cross Citation reads:

For extraordinary achievement while participating in an aerial flight over Ormoc Bay, Leyte, Philippine Islands, on 1 November 1944. This officer, while flying in a formation of eight P-38's over Ormoc Bay, encountered ten to fifteen enemy fighters. The P-38's attacked, and Lieutenant Castle opened fire on one of the hostile aircraft. The pilot bailed out and the airplane crashed near the shore line. Lieutenant Castle then fired a three-second burst at another fighter which passed in front of him, whereupon it started burning and later crashed and exploded. The outstanding courage and devotion to duty displayed by this officer are worthy of the highest commendation.