Citizens from Sarasota and Bradenton began work in 1939 to create a joint airport after two earlier unpaved Sarasota airports became obsolete. Beginning in 1940, development by the Works Progress Administration transformed 620 acres between U.S. 41 and Old Bradenton Road into a four-runway air field. During World War II, the U.S. Army Air Corps used the field as a training base. The 97th Bombardment Group, the first military group to use Sarasota Army Air Field, arrived from MacDill Field in Tampa in March 1942, lived in tents while tar-paper-covered barracks were built, and left in May to become the first U.S. Bomb Group to fly American planes in high-altitude daylight bombing raids from England. One of the pilots' instructors there was Captain Paul Tibbets, Jr., who later flew the B-29 Enola Gay in the mission that dropped the first atomic bomb on Hiroshima, Japan, helping bring the war in the Pacific to an end. As the 97th departed, the 92nd Bomb Group arrived, and during its short training period, group and squadron insignia were designed by Sarasota cartoonist V.T. Hamlin, who drew the "Alley Top" comic strip. After Works Progress Administration crews completed their work on the airport and repaired runways damaged by heavy B-17 bombers, more permanent buildings were constructed, and the Army Air Corps used the field for fighter pilot training until 1945, graduating an average of 70 pilots every 30 days. Approximately 60 airmen lost their lives there in training accidents during the war. In January 1946, the Sarasota Army Air Field was deactivated, turned over to the joint airport authority, and opened to civilian use as the Sarasota-Bradenton Airport. National Airlines, which had served the old municipal airport, resumed regular service to Sarasota in 1944. Civilian use expanded with a small control tower in 1957, a terminal in 1959, removal of old military buildings, and, in the 1960s, the addition of jet flights, an instrument landing system, runway extensions, high-intensity lighting, and additional airlines. A new terminal opened in 1989, and the airport was renamed Sarasota Bradenton International Airport when Port-of-Entry was granted in 1992.