The 131st Fighter Squadron, nicknamed the Barnestormers, is a unit of the Massachusetts Air National Guard 104th Fighter Wing located at Barnes Air National Guard Base, Massachusetts. The 131st is due to convert to the Lockheed Martin F-35A Lightning II in June 2026.

The squadron was first established in August 1942 at Bellows Field, Hawaii Territory as the 333d Fighter Squadron. It was initially part of the air defense of Hawaii, equipped with P-39 Airacobras. It also served as a Replacement Training Unit and flew reconnaissance patrols over Hawaii until late 1943.

The 333d deployed to the Central Pacific as part of the Thirteenth Air Force island hopping campaign against Japanese in late 1943. It engaged in combat with the Japanese until April 1944, returning to Hawaii and being re-equipped and trained with long-range P-51 Mustangs. The squadron redeployed to the Western Pacific, and was stationed on Iwo Jima while the battle for the island was still ongoing and engaged in long-range B-29 Superfortress escort missions over Japan. It continued that mission until the end of hostilities in August 1945. The unit moved to the Mariana Islands, as a Far East Air Forces fighter squadron, and was inactivated there in 1946.

The 333d Fighter Squadron was redesignated the 131st Fighter Squadron and was allotted to the Air National Guard on 24 May 1946. It was organized at Barnes Municipal Airport, Massachusetts, and was extended federal recognition on 24 February 1947. The squadron was equipped with P-47D Thunderbolts and was assigned to the Massachusetts National Guard 102d Fighter Group.

In 1950, the Massachusetts ANG converted to the wing-base (Hobson Plan) organization. As a result, the 67th Fighter Wing was withdrawn from the Air National Guard and inactivated on 31 October 1950. In its place, the 102d Fighter Group was assigned to the newly activated 102d Fighter Wing, however there was no change in mission to the 131st and it remained assigned to the 102d Fighter Group.

The mission of the 131st Fighter Squadron was the air defense of Massachusetts. With the surprise invasion of South Korea on 25 June 1950, and the regular military's lack of readiness, most of the Air National Guard was federalized placed on active duty. The 131st was retained by the Commonwealth of Massachusetts to maintain the air defense mission. In 1951, the F-47s were retired to Davis-Monthan Air Force Base and the 131st was re-equipped with the F-51H Mustang Very Long Range fighter. With its air defense mission, the 131st was redesignated as the 131st Fighter-Interceptor Squadron.

Beginning on 1 March 1953, the 131st placed two F-51H fighters and five pilots on air defense "runway alert" from one hour before sunrise to one hour after sunset. The runway alert program was the first broad effort to integrate reserve forces into a major Air Force operational mission on a volunteer basis during peacetime. In 1954, the Mustangs were reaching the end of their service lives, and the 131st entered the jet age when it received F-94A Starfire interceptors.

After the Korean War, the Massachusetts Air Guard began to modernize and expand. On 1 May 1956 the 102d wing was redesignated as the 102d Air Defense Wing and the Guard units at Barnes were authorized to expand to a group level, and the 104th Fighter Group (Air Defense) was established, with the 131st becoming the group's flying squadron. Other elements assigned into the group were the 104th Material Squadron, 104th Air Base Squadron, and the 104th USAF Infirmary. The 104th, along with the 102d Fighter Group (Air Defense) at Logan Airport, Boston began attending annual training at Otis Air Force Base.