made ready for overseas movement, personnel for these planes were also being processed. Pilots, co-pilots, navigators and crew chiefs were assigned as a crew for each aircraft. Paperwork was handled, necessary specific B-24 life support equipment was issued and some technical training for supporting the aircraft accomplished. Once production began, it became difficult to introduce changes dictated by field experience in the various overseas theaters onto the production line in a timely fashion. Consequently, newly constructed Liberators needed modifications for the specific geographic areas they were to be flown in combat. For this reason, a series of Air Technical Service Command modification centers were established for the incorporation of these required theater changes into new Liberators following their manufacture and assignments. There were seven known modification centers: Consolidated/Fort Worth; Oklahoma City Air Materiel Center at Tinker Field, Tucson Modification Center at Davis-Monthan Field; the Birmingham Depot in Alabama; the Northwest Airlines Depot in Minneapolis, Minnesota; the, Martin-Omaha manufacturing plant, and the Hawaiian Air Depot at Hickam Field. Ownership changes Although the airfield itself and the buildings to the east of the runways had been built on Henry Ford's personal property, it is unclear how the parcels across the county line that became the site of the bomber plant were assembled. In any event, Henry Ford (who, although technically retired from Ford Motor operations until his son Edsel's death from undulant fever in 1943, still held a say in company affairs) had insisted on building the factory without government financing. Instead, the company built the factory, and sold it to the Reconstruction Finance Corporation's Defense Plant Corporation (RFC-DPC), which then leased it back to Ford for the duration of the war. The land which held the airfield was transferred from Henry Ford's control to that of the company in July 1944, and sold to the RFC-DPC shortly thereafter. Postwar history See also Willow Run Transmission and Willow Run Assembly. Willow Run as Detroit's commercial airport Between 1946 and 1947, passenger airlines serving Detroit moved from Detroit City Airport on the city's crowded east side, to Willow Run; shortly thereafter, Wayne County officials began expanding Detroit-Wayne Major Airport at Romulus, which was closer to Detroit than Willow Run. Willow Run's relative isolation encouraged new approaches to passenger transportation to and from airports; at Willow Run in 1946, Warren Avis founded Avis Airlines Rent a Car Systems, the first rental car operation at