"It's a pretty limited pool of people," Groh said.
One possible candidate is board member Jim McNerney, who heads St Paul, Minnesota-based 3M Co but has experience in aerospace because he served as head of GE Aircraft Engines.
3M spokeswoman Jacqueline Berry said that was "speculation."
"Mr McNerney says he's very happy at 3M and has no plans to leave in the foreseeable future," she said.
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