President Obama walks over to greet well-wishers after stepping off Air Force One upon his arrival at  the Detroit Metropolitan Wayne County Airport in Romulus, Mich., on Monday, Dec. 10, 2012, before going to the Daimler Detroit Diesel plant in Redford. (AP Photo/Charles Dharapak)

Photo by: Charles Dharapak

President Obama walks over to greet well-wishers after stepping off Air Force One upon his arrival at the Detroit Metropolitan Wayne County Airport in Romulus, Mich., on Monday, Dec. 10, 2012, before going to the Daimler Detroit Diesel plant in Redford. (AP Photo/Charles Dharapak)