The Fresno Yosemite International Airport opened as a military airfield in June 1942, just six months after Japan's attack on Pearl Harbor, leading the United States to enter World War II. The new airfield was named Hammer Field and was used by the United States Army Air Forces as a training facility for the new pilots of the Fourth Air Force. It had a single northwest/southeast oriented runway with a length of 7,200 feet (now runway 11L/29R). Night fighter training, using Northrop P-61s, was moved to Hammer Field in January 1944, initially with the 481st Night Fighter Operational Training Group, replaced by the 319th Wing in May 1944. Training for the Bell P-59 Airacomet was added to the 319th mission in 1944, as well, confirmed Col. Ralph H. Snavely, commanding officer of the 319th Wing. At the time, civil and commercial aviation used Chandler Field that had opened in November 1929. Chandler is 1.5 miles (2.4 km) west of downtown Fresno, on a small site. Less than a decade after it opened, it was clear that the small runway at Chandler would not be able to accommodate coming larger airliners. After World War II, Hammer Field was inactivated by the Army Air Forces, and the city of Fresno saw an opportunity to use the site to create a commercial airport much larger than Chandler Field. In 1946, the War Assets Administration reallocated the property to the city, and the construction of a passenger terminal on the northeast side of the airfield was immediately begun. In 1948, the newly renamed Fresno Air Terminal (FAT) opened. Trans World Airlines (TWA) and United Airlines flights to San Francisco/Oakland and Los Angeles moved from Chandler Field to the newly opened airport. Chandler Field was retained by the city of Fresno as a reliever airport and continues to operate as the Fresno Chandler Executive Airport. Strategic Air Command facilities for Convair B-36 operations were initially proposed for “Hammer Air Force Base,” but objections from the City of Fresno led them to be changed to Travis Air Force Base instead. The Fresno upgrade was projected to cost $22.3 million. The California Air National Guard moved to the airport in the 1950s and established the Fresno Air National Guard Base on the southeast corner of the property. The guard also built munition storage bunkers along the northern edge of the airport grounds. The 194th Fighter Squadron moved to the facility in late 1954, followed by the 144th Fighter Wing in 1957. As the guard moved in, a second parallel runway (11R/29L) was constructed and opened to traffic in 1956. Construction started on a new, larger passenger terminal in 1959 on the south side of the field. The building was a long, simple shape that housed a baggage claim area, a central lobby, and a ticketing area. The $1.5 million terminal had long walls of glass for the baggage claim and the ticketing areas, which book-ended the central lobby of solid masonry block which bears a venetian glass mosaic called "Sky and Ground" from Raymond Rice. From the central lobby, passengers used a tunnel to reach the open-air, remote concourse where they boarded planes from ground level. The terminal opened on March 28, 1962 and shortly after received an award from the San Joaquin Valley Chapter of the American Institute of Architects. Although renovated, the original terminal building is still in use today for the same functions that it was designed for. The current air traffic control tower was built around the same time as the terminal and opened in 1961. Pacific Air Lines was first to schedule jets to Fresno, with Boeing 727-100s in 1966. United was the dominant carrier at the airport throughout the mid-1970s. At the airlines' peak, United operated daily DC-8s jet service to Denver, San Francisco and Los Angeles. Hughes Airwest and PSA jets also served the airport at this time. The first significant expansion to the passenger terminal came in 1978 when a concourse was built straight out from the central lobby.