After the United States entered the war, several squadrons of the 35th Pursuit Group in the Philippines became total losses in combat and the newly trained squadrons of the 31st PG, including the 41st PS, were detached on January 15, 1942, to form the core of a new 35th Group and moved to the West Coast for immediate deployment to the Pacific.
The U.S. Army Air Forces then created three new squadrons to become the flying units of the 31st fighting Group
On January 30, 1942, 1st Lt.
Thyng became the first commanding officer of the newly created 309th Fighter Squadron, 31st Fighter Group.
Initially equipped with Curtiss P-40B Warhawk fighters, the 309th FS relocated to New Orleans to transition to the P-39, and trained during the spring of 1942 for deployment overseas to England.
Thyng was promoted to captain on April 4.
In May, it staged to Grenier Field, New Hampshire, to train for long-distance over-water flights using drop tanks, for which the P-39 was found to be unsuitable.

The headquarters and ground echelon of the 309th FS shipped out to England on June 4, 1942, aboard HMS Queen Elizabeth as part of Operation Bolero.
Arriving at its new base at High Ercall without aircraft on June 11, the squadron began flight training on Spitfire V fighters provided by the RAF beginning June 26.
Its RAF instructors declared the 31st FG ready for operations in late July, the first U.S. combat group to be so rated.
On July 26, the group headquarters and its three-squadron commanders, including Major Thyng, flew a combat mission with No.
412 Squadron (RCAF) based at RAF Biggin Hill, a fighter sweep near Saint-Omer, France, that resulted in the loss of one 31st FG Spitfire.

Thyng's 309th FS was relocated twice, first to RAF Warmwell, Dorset, in late July, and then to RAF Westhampnett, Sussex, on August 4, where it became operational, flying its first operational mission the next day.
Its scheduled missions were "Rodeos", feints to decoy German fighter opposition, and convoy escorts, but on August 9 Major Thyng and a wingman flew a defensive patrol over the English Channel in which Thyng claimed a Junkers Ju 88 damaged, the first claim by a U.S. fighter during the war.
His personal aircraft was a Spitfire V he nicknamed Mary & James after his wife and son, bearing the squadron identification codes WZ—A.
On August 19, 1942, the 31st Fighter Group flew eleven missions and 123 sorties in support of Operation Jubilee, the Allied raid on Dieppe, France.
There it encountered its first opposition from Luftwaffe fighters and recorded its first kills.
Thyng was granted a "probable" kill of an Fw 190 and was awarded the Silver Star for flying top cover for a rescue mission of a downed 31st FG pilot.

On August 20 the 309th FS conducted the first American escort mission for U.S. B-17 Flying Fortress bombers, and on August 29 the 31st FG flew its first group mission.
The 31st flew several days of escort missions for U.S. Douglas A-20 light bombers at the beginning of September, and then stood down from operations except for defensive reactions until a final escort mission on October 2, its last before transferring to the Twelfth Air Force.

On October 26, 1942, the 31st shipped its Spitfires by sea to Gibraltar, to provide air support for Operation Torch as part of the Twelfth Air Force.
After the United States entered the war, several squadrons of the 35th Pursuit Group in the Philippines became total losses in combat and the newly trained squadrons of the 31st PG, including the 41st PS, were detached on January 15, 1942, to form the core of a new 35th Group and moved to the West Coast for immediate deployment to the Pacific. The U.S. Army Air Forces then created three new squadrons to become the flying units of the 31st fighting Group
On January 30, 1942, 1st Lt. Thyng became the first commanding officer of the newly created 309th Fighter Squadron, 31st Fighter Group. Initially equipped with Curtiss P-40B Warhawk fighters, the 309th FS relocated to New Orleans to transition to the P-39, and trained during the spring of 1942 for deployment overseas to England. Thyng was promoted to captain on April 4. In May, it staged to Grenier Field, New Hampshire, to train for long-distance over-water flights using drop tanks, for which the P-39 was found to be unsuitable.
The headquarters and ground echelon of the 309th FS shipped out to England on June 4, 1942, aboard HMS Queen Elizabeth as part of Operation Bolero. Arriving at its new base at High Ercall without aircraft on June 11, the squadron began flight training on Spitfire V fighters provided by the RAF beginning June 26. Its RAF instructors declared the 31st FG ready for operations in late July, the first U.S. combat group to be so rated. On July 26, the group headquarters and its three-squadron commanders, including Major Thyng, flew a combat mission with No. 412 Squadron (RCAF) based at RAF Biggin Hill, a fighter sweep near Saint-Omer, France, that resulted in the loss of one 31st FG Spitfire.
Thyng's 309th FS was relocated twice, first to RAF Warmwell, Dorset, in late July, and then to RAF Westhampnett, Sussex, on August 4, where it became operational, flying its first operational mission the next day. Its scheduled missions were "Rodeos", feints to decoy German fighter opposition, and convoy escorts, but on August 9 Major Thyng and a wingman flew a defensive patrol over the English Channel in which Thyng claimed a Junkers Ju 88 damaged, the first claim by a U.S. fighter during the war. His personal aircraft was a Spitfire V he nicknamed Mary & James after his wife and son, bearing the squadron identification codes WZ—A.
On August 19, 1942, the 31st Fighter Group flew eleven missions and 123 sorties in support of Operation Jubilee, the Allied raid on Dieppe, France. There it encountered its first opposition from Luftwaffe fighters and recorded its first kills. Thyng was granted a "probable" kill of an Fw 190 and was awarded the Silver Star for flying top cover for a rescue mission of a downed 31st FG pilot.
On August 20 the 309th FS conducted the first American escort mission for U.S. B-17 Flying Fortress bombers, and on August 29 the 31st FG flew its first group mission. The 31st flew several days of escort missions for U.S. Douglas A-20 light bombers at the beginning of September, and then stood down from operations except for defensive reactions until a final escort mission on October 2, its last before transferring to the Twelfth Air Force.
On October 26, 1942, the 31st shipped its Spitfires by sea to Gibraltar, to provide air support for Operation Torch as part of the Twelfth Air Force.
Harrison Thyng