General Motors to close or idle 12 more plants Monday, June 1st, 2009 at 7:22am EST AP Photo/Carlos Osorio DETROIT General Motors Corp. says it will permanently close nine more plants and idle three others to trim production and labor costs under bankruptcy protection. Assembly plants in Pontiac, Mich., and Wilmington, Del., will close this year, while plants in Spring Hill, Tenn., and Orion, Mich., will shut down production but remain on standby. Powertrain plants in Livonia, Flint and Ypsilanti Township, Mich. will close next year, along with plants in Parma, Ohio, and Fredericksburg, Va. Stamping plants in Indianapolis and Mansfield, Ohio, also will close. A stamping plant in Pontiac, Mich., will be idled but remain in a standby capacity. GM says it will also close service and parts warehouses in Boston, Jacksonville, Fla., and Columbus, Ohio, by the end of this year.