In an internet conversation this week with Sir Richard Branson, Mr Musk said: “I originally started thinking about it when I read a thing about California’s high speed rail project, which was somewhat disappointing. It is actually worse than taking the plane. I get a little sad when things are not getting better in the future.

“Another example would be like the Concorde being retired and the fact there is no supersonic passenger transport. I think that is sad. You want the future to be better than the past, or at least I do.

“The Hyperloop is something that would go effectively faster than the speed of sound. Conceivably you could live in San Fran and work in LA.”

Mr Musk said the Hyperloop would be best used between paired cities less than 1,000 miles apart, and would be safer than air travel.