PSP was built as a United States Army Air Corps emergency landing field in 1939 on land owned by the Agua Caliente Band of Cahuilla Indians due to its clear weather and its proximity to March Field and the Los Angeles area. In March 1941, the War Department certified improvements to the existing airport in Palm Springs as essential to National Defense. The airport was approved to serve as a staging field by the Air Corps Ferrying Command 21st Ferrying Group in November 1941. Land was acquired to build a major airfield a half mile from the old airfield site. The new airfield, Palm Springs Army Airfield, was completed in early 1942, and the old air field was then used only as a backup. Many of the field's Air Transport Command 560th Army Air Forces Base Unit personnel stayed at the comfortable Lapaz Guest Ranch nearby. Training conducted at the airfield was by the 72d and 73d Ferrying Squadrons in long-distance over-water flying and navigation. Later, training was also provided to pursuit pilot training by IV Fighter Command 459th Base Headquarters and Air Base Squadron. Training was in P-51 Mustangs, P-40 Warhawks and P-38 Lightnings. On June 1, 1944, training moved to Brownsville Army Airfield, Texas, and the airfield was used for Army and Navy transport flights until the end of April 1945. The auxiliary field or backup field was declared surplus on May 12, 1945, and the main airfield was declared excess and transferred to the War Assets Administration for disposal in 1946 and it was sold to private buyers. The City of Palm Springs purchased the land in 1961 and converted it to Palm Springs Municipal Airport. Palm Springs had scheduled passenger service in 1934 operated by Palm Springs Air Lines with Ford Trimotor aircraft with flights to the Union Air Terminal (now the Hollywood Burbank Airport) in Burbank. Western Airlines flights began by 1943 followed by Bonanza Air Lines by 1955. Service was operated through the Thermal, California Airport. Bonanza reportedly moved to the Palm Springs Airport on December 15, 1957. In 1964, Western Lockheed L-188 Electras flew nonstop to Las Vegas, Los Angeles and San Diego. Bonanza and successors Air West and Hughes Airwest served Palm Springs for many years with the Fairchild F-27 followed by Douglas DC-9s. American Airlines Boeing 707s appeared in winter 1967–68. By 1969, American had four Boeing 707 departures a day from the airport, two nonstops to Los Angeles and two nonstops to Phoenix and on to Chicago. Trans World Airlines (TWA) Boeing 707s arrived in 1978, flying to Chicago via Phoenix. Scheduled nonstops did not reach beyond California, Las Vegas, and Phoenix until winter 1969–70, when American Airlines started a nonstop to Chicago O'Hare Airport. In the 1970s, American McDonnell Douglas DC-10s appeared, the largest aircraft ever scheduled to PSP. In 1976, American was flying the DC-10 to New York LaGuardia Airport via Chicago O'Hare Airport as well as Boeing 727-100s to Dallas/Fort Worth, Phoenix and Los Angeles. In 1976 Western Boeing 727-200s and Boeing 737-200s flew nonstop to Las Vegas, Los Angeles and San Francisco. In 1987, Western was merged into Delta Air Lines which continues to serve PSP with year-round service to Salt Lake City (via Delta Connection) and seasonal service to Atlanta, Minneapolis-St. Paul, and Seattle. Other jet service to Palm Springs in the past included flights operated by Air21, Air California and successor Air Cal, America West Airlines, CP Air, the original Frontier Airlines (1950–1986), Hughes Airwest, Morris Air, Pacific Express, Pacific Southwest Airlines (PSA), Pan Am, Reno Air, Republic Airlines (1979–1986) and USAir.