The second of the public-private partnerships is Building 9001, originally known as the Tinker Aerospace Complex housed in the former General Motors Oklahoma City Assembly Plant located west of the runway on the south side of the base, north of I-240. A 50-year lease-purchase agreement was executed in September 2008 between Oklahoma County and the Air Force, covering the 2.5 million square foot (353,000 m²) facility and . Previously, the largest single building at the base was Building 3001 at . Tinker has leased about 4/5 of the facility and will host some current 76th Maintenance Wing operations as well as other Department of Defense missions, including work on the C-17 engines, joint strike fighter engines and core work on the new KC-46 tanker. Work being transferred to the complex is currently being done at 69 separate facilities on base, many of which are World War II-era temporary buildings located in runway clear zones. Burlington Northern Santa Fe provides a rail spur into the complex.