|Occupying force:|| Construction of Hilo Airport, a commercial airport on the east coast of the island of Hawaii, commenced in 1927. The site was known as Keaukaha. Inmates from a nearby prison camp cleared the area of brush and rocks and the new facility was dedicated on 11 February 1928. The following year, Inter-Island Airways (now Hawaiian Airlines) began flights from Honolulu to Hilo. Improvements to Hilo\'s airfield were minimal during its first decade however, between 1937 and 1941, the U.S. government invested over US$575,000 (US$9.28 million in 2011 dollars).
The U.S. began a buildup of the armed forces in late 1940. In March 1941, the U.S. Army Air Corps [redesignated U.S. Army Air Forces (USAAF) on 20 June 1941] began construction of facilities for military use at this airfield. The field was not attacked by the Japanese on 7 December 1941 but martial law was ordered for all islands and all airports in the Hawaiian Islands came under the control of the U.S. military. This airfield was taken over by the USAAF on 25 December 1941.
In 1942, the USAAF began work to convert the airport to a major base. Construction resulted in three paved runway, 6,500-, 6,000- and 3,000-feet (1,981, 1,829 and 914-meters) long. On 1 April 1943, Hilo Army Air Field was officially established by the USAAF. On 19 April, the Territorial Legislature renamed Hilo Airport General Lyman Field, for General Albert Lyman (1885–1942), the first U.S. General of Hawaiian ancestry.
By 1944, General Lyman Field was a main USAAF fighter base under the jurisdiction of the Seventh Air Force and the Air Transport Command with parking for 38 fighters.
In June 1942, U.S. Navy planes to support future operations were pouring into the Pearl Harbor area from the U.S. Critical construction materials were at a premium, and it was necessary, as far as possible, to disperse air facilities, both for convenience of operation and as a precaution against possible renewal of Japanese air attacks. With these factors in mind, Admiral Chester W. Nimitz, Commander in Chief of the Pacific Fleet, directed a joint board of Army and Navy officers to submit recommendations for the location of an airfield to support the operation of two aircraft carrier groups totaling 180 aircraft. After investigating the existing facilities at Hilo Army Air Field, the board recommended that it be expanded to meet the Navy needs.
Construction was undertaken by the Seabees, which arrived in March 1943. Runways were widened from 200-to-500-feet (61-to-152-meters), and additional parking areas built.
Naval Air Station Hilo was commissioned on 1 August 1943 although it was only 20 percent complete.
By October 1943, the threat of Japanese attack had subsided and the USAAF withdrew their fighter squadron and planned to base heavy bombers here in the summer of 1944. However, the plan changed and the bombers were based on Oahu. The USAAF’s Air Transport Command used this base but otherwise, it was totally a Navy base. The Navy used NAS Hilo as a training base for Navy aircraft units preparing for operations in the Pacific. These units generally spent two months here before boarding a carrier.|