Lynch joined the United States Army Air Corps and after completing pilot training was assigned to the 39th Pursuit Squadron in March 1941 at Selfridge Field, Michigan, flying the Bell P-39 Airacobra. The squadron spent most of the year training.
Lynch was sent to Australia with the squadron in early 1942. The squadron soon moved up to Port Moresby. On 20 May, Lynch claimed his first two victories. A third followed on 26 May, while Lynch and other pilots from the squadron escorted a troop transport flight. On 15 June, Lynch was forced to bail out after his plane was heavily damaged by Japanese aircraft, breaking his arm in the process. In June, the squadron was selected to become the first Fifth Air Force P-38 squadron, and after reequipping with the new aircraft was back in combat from November, operating out of Laloki airfield. On 27 December, Lynch became an ace after he shot down two Nakajima Ki-43 Oscars over the Buna beachhead. For this action, which resulted in the breaking up of an attempted Japanese bombing raid, he was awarded the Distinguished Service Cross. He claimed two more Mitsubishi A6M Zeroes on 31 December during a bomber escort mission to Lae. On 6 January 1943, P-38s from the squadron bombed a Japanese reinforcement convoy bound for Lae. Lynch claimed a possible bomb hit on one ship. Lynch downed a Ki-43 while escorting Curtiss P-40 Kittyhawks on their way to bomb the Lae convoy on the next day. On 3 March, he claimed another Zero during the Battle of the Bismarck Sea. On 24 March, Lynch became commander of the 39th Fighter Squadron. On the afternoon of 8 May, he shot down a "Hamp". Lynch claimed another victory on 12 June. He was promoted to major in July. While on a bomber escort mission to Wewak, he claimed two Kawasaki Ki-45 Nicks on 20 August. On 21 August, he downed another Japanese aircraft. Lynch became one of the first in the South West Pacific to shoot down a Kawasaki Ki-48 Lily bomber on 4 September over the Huon Gulf. On 16 September he claimed his sixteenth victory. Lynch took a 30-day leave in October, marrying his college girlfriend, Rosemary Fullen, in Swissvale on 23 October. Lynch returned to combat in January, assigned to V Fighter Command alongside fellow top-scoring ace Richard Bong. Bong and Lynch were allowed to "free-lance" for the next months. On 10 February 1944, Lynch claimed a victory in the Wewak area. On 15 February Lynch covered Bong while he downed a Kawasaki Ki-61 Tony on a flight back from an escort mission to Kavieng. On 28 February, he also covered Bong while he destroyed a Japanese transport possibly carrying senior officers on the Wewak runway. After this mission, Lynch was promoted to lieutenant colonel. He claimed two more victories on 3 March. Lynch claimed his twentieth and last victory on 5 March.
Death
On 8 March, Lynch and Bong strafed barges in Aitape harbor. After setting one on fire on their first pass, they returned for a second pass when Lynch's P-38 was hit in the engine. Lynch's plane began to burn and he bailed out too close to the ground for his parachute to deploy. His remains were never found.
Military decorations
Lynch earned the following decorations:
Aerial victory credits
The data in the following table is from Newton and Senning.
