You can imagine that Elon Musk doesn’t have a lot of free time, you don’t get to be in his position by having a lot of free time on your hands, and it’s likely that the doesn’t have much of it after splitting time between Tesla and SpaceX. He did work on a high-speed mass transportation system called Hyperloop but is open to let other people take it further, and it turns out that he even has a design for a supersonic electric jet in his mind but not enough time on his hands to seriously develop it.
Musk has talked about electric jets in the past and one could assume that he has played around with the idea, which he has, his idea is for a supersonic electric jet capable of vertical takeoff.
He was asked in an interview recently what he would be doing if he wasn’t running Tesla, to which Musk replied that he liked the idea of an electric aircraft company, “I do think one could do a pretty cool supersonic, vertical takeoff and landing electric jet.”
The host asked Musk if he was just making things up, “No, I have a design in mind for that,” Musk said, while pointing out that he has too many things on his plate to do with both Tesla and SpaceX, and then there’s Hyperloop as well.
Eventually Musk was asked about whether he would consider handing over one of the two companies he heads right now to free more time up for himself, he expects to be with SpaceX and Tesla for “as long of the future as I can imagine,” but it will inevitably happen in the long term because he will either be “retired or dead.”