Electric cars and and commercial spaceflight are clearly not enough. Tesla and SpaceX CEO Elon Musk said he’s mulling how to provide super-convenient, electric-powered air travel.

When asked to reveal his “next great idea” during a brief Q&A session this week, Musk answered: “Well I have been thinking about the vertical takeoff and landing electric jet a bit more. I mean, I think I have something that might close. I’m quite tempted to do something about it.”

Neither the idea of an electric jet or a plane with the capacity for vertical take off and landing is revolutionary by itself. In June 2015, an electric aircraft crossed the English Channel for the first time. Meanwhile, Denver-based XTI Aircraft Company has been raising money to prototype a vertical-takeoff airplane, which the company says could be ready in three years. And Solar Impulse 2, a solar-powered aircraft, set a record in 2015 by crossing the Pacific Ocean.

Musk first mentioned combining the two concepts last fall.

“I do like the idea of an electric-aircraft company. I think one could do a pretty cool supersonic, vertical takeoff and landing electric jet. That would be really fun… I have a design in mind for that,” he told Marketplace in Oct. 2015.

Addressing students this week, he hinted that he may be ready to take it a step further. After comparing the concept of a vertical takeoff electric plane to his initial plans for SpaceX, Musk added: “I think, ultimately, seeing is believing. Seeing physical hardware moving and doing useful things, that’s what convinces people.”