Former Pennsylvania Sen. Rick Santorum speaks at the Bella Donna Chapel in McKinney, Texas, on Wednesday. Rex C. Curry/Associated Press hide caption

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The best airplane mechanics are skilled at everything from metal part fabrication to electronics to lavatory plumbing. Other, better-paying companies soon become interested in their skills. Courtesy AAR hide caption

itoggle caption Courtesy AAR

A worker stands next to an array of Sharp solar cell modules at a power plant south of Tokyo in August. Sharp was one of 1,400 solar panel manufacturers in attendance at the Solar Power International conference, where industry optimism was high.

Toshifumi Kitamura/AFP/Getty Images hide caption

itoggle caption Toshifumi Kitamura/AFP/Getty Images