Elon Musk has been seriously thinking about an electric jet

We already know that Elon Musk is the king of electric cars. He's gunning to become the king of electric planes, too.

The CEO of Tesla Motors and SpaceX spoke at the Hyperloop Pod Competition this week about his bigger plans for electrification beyond ground mobility.

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"I have been thinking about the vertical takeoff and landing (VTOL) electric jet a bit more," Musk said. "I think I have something that might be close. I'm quite tempted to do something about it."

This isn't the first time Musk has mentioned electric-powered airplanes; he spoke about planes in 2009, and has mused about the idea at other times, most recently in the fall. While it looks like it's still just an idea, the frequency at which Musk is talking about it suggests it's occupying more space in his head than it used to.

And he's not the first to consider electric power for air travel, either. Electric passenger planes have been around since the 1970s, but they haven't exactly gained traction — mostly due to the big obstacle of battery technology. Jet fuel is much cheaper than batteries, especially the lightweight ones required for air travel.

However, there are some aircraft, such as the 787 and A350, that use battery power to run various aircraft systems, from flight software to wing surfaces such as flaps and spoilers. However, what Musk is imagining is an all-electric airplane.

Though fully electric planes have vexed designers for decades, if anyone can sort it, it's probably Musk. Once Tesla's battery-producing Gigafactory is running at full tilt, it will be producing a glut of inexpensive and energy-rich lithium-ion batteries, some of which could theoretically make their way into the wings of planes... one day.