Aerospace engineers have been working in a Mojave desert hangar for four years, fashioning a commercial spaceship to loft rich tourists some 62 miles above Earth.

Now the wraps come partially off the top-secret project.

British billionaire Sir Richard Branson and American aerospace designer Burt Rutan are due on Monday to show off their mothership, which is designed to air launch a passenger-toting spaceship out of the atmosphere.

More than 250 wannabe astronauts have paid $200,000 or put down deposits for a chance to float weightless for a mere five minutes.

"Having invested all my faith in it, I'm so excited to see the actual thing," said artist Namira Salim, a customer who is lined up for a ride on Branson's Virgin Galactic.