Airlines aren’t the worst polluters in the world, but planes do account for an incredible 2.5% of the world’s carbon emissions. So by any measure, flying is a privilege—the exact sort of 21st-century excess that we need to reassess. Which is why the strategic design consultancy Manyone is thinking about radical alternatives to flight. The studio’s solution? A giant train that loops around half the world like a mega subway system.

Dubbed the AeroSlider, it’s an elevated train line that passes through a series of unobtrusive magnetic loops instead of running on a track. Much like the principles behind a rail gun, the loops speed up the train sequentially, propelling it up to speeds of 500 mph—or the average speed of a plane. It was conceived by creative director Jens Martin Skibsted.

The core design is, admittedly, something of an engineering fantasy.

But as lead designer Guillermo Callau explains to me, the team has actually put a lot of thought into the feasibility of the route, which passes from Africa to Europe to Asia, to the cars, which feature everything from typical seats to a large shared indoor garden. The idea isn’t to present a completely realized design, but to think bigger about how to reduce our reliance on flying.

“You would take something a little slower than a flight, but it would be immensely more efficient,” says Callau. “This isn’t just being optimistic. It’s necessary. CO2 tariffs, or taxes on CO2, will make flights way more inaccessible.”

Let’s start with the track, which is not really a track at all, but a series of magnetic pylons. This design would drive a train forward much like a bullet; the train’s body would need to be aerodynamic and respond to magnetic forces, but it wouldn’t require any onboard motors or batteries to drive it. Those pylons could be easily installed, too. While train tracks require vast amounts of careful leveling to manage even small hills, pylons could be stuck deeper or less deep into the ground to create a level track. They could even eliminate the need to build bridges to cross short bodies of water, since the train floats in the air.

This 65-foot-tall line would not prevent animals from crossing underneath it, as some highways and train tracks do. The route can even turn, in theory. While the pylons appear to be arranged in perfect circles in the images here, Callau proposes they could be elliptical, which would offer a bit of left-right leeway, allowing the train to turn very slowly. “Within two kilometers it can turn four degrees, or something like that,” he says. In fact, high-speed rails of today have similar restrictions.