This weekend, Richard Branson will be taking a rocket-powered space plane on a 2,400 mph (3862.43 kmh) ride to the edge of space. If everything goes according to plan, he will be the first billionaire that has travel to space. That is, if EVERYTHING goes smoothly. 

But experts have chalked up a number of things that could go haywire. For instance, the rocket motor could fail to light up. The cabin could lose pressure and threaten the passengers’ lives. And the intense physics involved when hurtling out of — and back into — the Earth’s atmosphere could tear the vehicle apart.

Branson will be following the footsteps of the test pilots and Virgin galactic employees who have already flown on VSS Unity the vehicle Branson’s company, Virgin Galactic, has spent nearly two decades working to develop.

Still, Virgin Galactic has built safety backstops into its spaceplane, completed more than 20 test flights, three of which have successfully reached the edge of space, received the go-ahead from an internal safety review board and a green light from federal regulators to host passengers. Any time humans are on an airborne vehicle, there’s risk involved.