The U-3A is the military variant of the civilian Cessna Model 310. The 310 first flew in 1953 with the first deliveries beginning the following year. The 310 proved very successful in the civil market and was chosen by the Air Force in 1957 for use as a light utility transport. Initially called the L-25A approximately 160 were ordered in 1957 and 1958, a further 30 were ordered in 1960 with more powerful engines and called L-27B. The designation of these aircraft was changed in 1962 to U-3A and U-3B.
A number of military surplus U-3 aircraft found their way into the hands of civilians and other government agencies after their military service. The Forest Service acquired this aircraft for use as a “lead plane” in fighting forest fires. The job of a lead plane is to fly ahead of the large fire bombers and safely direct them to their drop points.
United States Department of Agriculture, Forest Service, 1971
Pima Air & Space Museum