Elon Musk is in the rare position of being CEO of two public companies.

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The noise around a Tesla-SpaceX mega-merger is growing louder.In an interview with CNBC aired Friday, SpaceX president Gwynne Shotwell said the two Elon Musk-led companies are working toward the same goals — and didn't rule out a merger in the future."That might make Elon's life a little easier, actually," said Shotwell, who has been SpaceX president since 2008."There's no question that there's synergies between Tesla and SpaceX in our futures, definitely, there's a convergence of a kind of what we're all trying to accomplish in the future," she said.However, Shotwell added that she was focused on "keeping the lights on" at SpaceX and the company's ambitious expansion plans, rather than any tie-up with Musk's other major public company."I'm not focused on that part of the future, at least," she said.

SpaceX president and COO Gwynne Shotwell.

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