SpaceX CEO Elon Musk unveiled revised plans to travel to the Moon and Mars at a space industry conference today, but he ended his talk with a pretty incredible promise: using that same interplanetary rocket system for long-distance travel on Earth. Musk showed a demonstration of the idea onstage, claiming that it will allow passengers to take “most long-distance trips” in just 30 minutes, and go “anywhere on Earth in under an hour” for around the same price as an economy airline ticket.

Musk proposed using SpaceX’s forthcoming mega-rocket (codenamed Big Fucking Rocket or BFR for short) to lift a massive spaceship into orbit around the Earth. The ship would then settle down on floating landing pads near major cities. Both the new rocket and spaceship are currently theoretical, though Musk did say that he hopes to begin construction on the rocket in the next six to nine months.

In SpaceX’s video that illustrates the idea, passengers take a large boat from a dock in New York City to a floating launchpad out in the water. There, they board the same rocket that Musk wants to use to send humans to Mars by 2024. But instead of heading off to another planet once they leave the Earth’s atmosphere, the ship separates and breaks off toward another city — Shanghai.

Just 39 minutes and some 7,000 miles later, the ship reenters the atmosphere and touches down on another floating pad, much like the way SpaceX lands its Falcon 9 rockets at sea. Other routes proposed in the video include Hong Kong to Singapore in 22 minutes, London to Dubai or New York in 29 minutes, and Los Angeles to Toronto in 24 minutes.

This proposed method of Earth-city-to-Earth-city travel would be, by far, the fastest ever created by humanity. The ship would reach a speed of about 18,000 miles per hour at its peak, Musk said, which is more than an order of magnitude faster than the Concorde.

Musk presented the idea at the very end of his speech, so he was light on details when it comes to the other logistics surrounding this proposal. (In fact, most of Musk’s speech was about how he wants to use this new rocket system to make all current and forthcoming Falcon rockets obsolete.) Using the numbers he showed earlier in the talk when describing the ship’s capacity with regards to the Moon and Mars, we can estimate it could carry somewhere between 80 and 200 people per trip. But we don’t know other basics like how much of the air travel market Musk sees this occupying, how it would be regulated, or even when SpaceX might attempt such a feat.

We also don’t know what the passenger experience would be like, and that’s an important factor in an idea like this. The thought of blasting off on a rocket to space is exciting, as is the potential for adding moments of weightlessness to your trip to London or wherever. But will people actually be willing to put their bodies through these kinds of extreme stresses for the sake of shaving a few hours off their trip?

And then there’s the landing. Despite occasional hiccups, airplanes land with overwhelming success. To its credit, SpaceX has gotten really good at landing its Falcon 9 rockets both on land and at sea, and Musk even began his speech by touting how 16 of them have landed successfully in a row. But the difference between landing a 14-story rocket booster with no passengers and a large ship full of them is one Musk will hopefully expound upon, either during another presentation or the next time he opens Twitter.