The Fairchild F-24 gained great popularity in the civilian market and were eagerly purchased by businessmen. In 1936, the US Navy purchased Fairchild F-24 aircraft and used them under the designations GK-1 and JK-1. It was also used by the US Army as a light transport aircraft and by the United States Coast Guard (Coast Guard) under the designation J2K. Also, the Civil Air Patrol air formation used a large number of Fairchild F-24 aircraft armed with 2 bombs. They were used to carry out patrol flights against German submarines off the east coast of the US in the early stages of World War II. The UC-61 aircraft were supplied to the US Navy as the GK-1 and to the UK, where they were used under the Fairchild “Argus” name. In 1941, the USAAF ordered 163 UC-61 aircraft, but under the Lend-Lease Act, 161 of them were shipped overseas. Under this program, 525 ex. UC-61 were delivered to the UK, where they received the designation “Argus” Mk.I and “Argus” Mk.II. They were assigned to the newly formed RAF- Air Transport Auxiliary command. 306 exemplars of the “Argus” Mk.III version were also delivered. In British aviation, most of the “Argus” aircraft were used in the Air Transport Auxiliary, serving on service flights and transporting airmen from operational airfields to Maintenance Units for equipment repair and delivery.