Virgin Galactic, a Virgin Group company, has sold some 200 tickets to passengers for suborbital flights, starting in 2008, said Will Whitehorn, the company's president.
It has collected 8.5 million pounds (US$15.6 million, euro12.4 million) in deposits for the flights that cost 109,000 pounds (US$200,000, euro158,000).
"Right now we're headed right on schedule," Whitehorn said. "Things are looking good from our perspective."
The venture by Virgin Group, owned by British billionaire Richard Branson, is building five spaceships and two airplanes by 2010.
Travelers will take seats in a spaceship that will be attached to a separate airplane. Following takeoff, the spaceship detaches itself from the plane at about 15,000 meters (49,000 feet) from the ground.
It then enters suborbital space for about 15 minutes _ including five minutes of weightlessness.
After its journey into space _ at 87 miles (140 kilometers) above Earth, it returns to the ground.
The total flight-time is about 2 hours and 15 minutes, and the voyages will initially launch from the Mojave Desert near Los Angeles before relocating to a permanent base in New Mexico in 2010.
Virgin Galactic is one of many companies venturing into space travel. Space Adventures, a Vienna, Virginia-based company, has already sent three people on a Russian Soyez rocket to the International Space Station, some 220 miles (360 kilometers) from Earth. Each trip costs 10.9 million pounds (US$20 million, 15.8 million euros).