Kansas City Industrial Airport was built after the Great Flood of 1951 destroyed the facilities of both of Kansas City's airlines, Mid-Continent Airlines and TWA, at Fairfax Municipal Airport. The facilities were across the Missouri River from the city's main Kansas City Municipal Airport, which was not as badly damaged. TWA's main overhaul base was a former B-25 bomber factory at Fairfax, and TWA commercial flights flew out of the main downtown airport. Subsequently Kansas City planned to build an airport with room for 10,000-foot (3,000 m) runways and knew the downtown airport would not be large enough. Kansas City already owned Grandview Airport south of the city with ample room for expansion, but the city chose to build a new airport north of the city away from the Missouri River following lobbying by Platte County native Jay B. Dillingham, president of the Kansas City Stockyards, which had also been destroyed in the flood. TWA moved its Fairfax plant to the new airport and also its overseas overhaul operations at New Castle County Airport in Delaware. The site just north of the then-unincorporated hamlet of Hampton, Missouri, was picked in May 1953 (with an anticipated cost of $23 million) under the guidance of City Manager L.P. Cookingham. Ground was broken in September 1954. The first runway opened in 1956; at about the same time the city donated the southern Grandview Airport to the United States Air Force to become Richards-Gebaur Air Force Base. TWA's Kansas City Overhaul Base at its peak in the 1960s and 1970s was Kansas City's largest employer, with 6,000 employees. Although Mid-Continent merged with Braniff in 1952, Kansas City named the new airport on the basis of Mid-Continent's historic roots of serving the Mid-continent Oil Field. Mid-Continent had renamed from Hanover Airlines in 1938 after moving its headquarters from Sioux City, Iowa, to Kansas City when it began service to Tulsa and other cities in the oil field. In 1954, TWA signed an agreement to move its overhaul base to the airport; the city was to build and own the $18 million-base and lease it to TWA. However, the downtown airport continued to be Kansas City's passenger airport; a 1963 Federal Aviation Agency memo called the downtown airport "one of the poorest major airports in the country for large jet aircraft" and recommended against spending any more federal money on it. Along with the cramped site, there were doubts that the downtown site could handle the new Boeing 747. Jets had to make steep climbs and descents to avoid the downtown skyscrapers on the 200-ft (60-m) Missouri River bluffs at Quality Hill, east of the approach course a mile or two south of the south end of the runway, and downtown Kansas City was in the flight path for takeoffs and landings, resulting in the constant roar of aircraft engines being heard downtown. In contrast, Mid-Continent was surrounded by open farmland. On July 1, 1965, Continental Airlines Flight 12 overran the runway while landing at Kansas City Municipal Airport. The Civil Aeronautics Board determined that the pilots of the Boeing 707 had landed properly within the touchdown zone for their ILS approach, and despite using the aircraft’s spoilers, thrust reversers, and wheel brakes, the remaining runway distance was too short for them to safely stop in heavy rain and tailwind conditions. Though having attempted to improve the runway surface and braking performance, the Airline Pilots Association said that many commercial pilots continued to "blacklist" the airport. A new airport, with longer runways, would be required to satisfy regulatory runway safety area requirements. In 1966, voters in a 24:1 margin approved a $150 million bond issue following a campaign by Mayor Ilus W. Davis to move the city's main airport to an expanded Mid-Continent.