Work has started on a new Virgin Galactic spaceship after the original craft broke up and crashed on a test flight in October, killing one of its pilots.
SpaceShipTwo is designed to reach the edge of space at an altitude of 100km, or 62 miles, before returning to Earth. More than 700 individuals have signed up to pay about $250,000 (£163,467) for a ticket.
The second "SpaceShipTwo" sub-orbital space plane could fly later this year, according to reports.
Virgin chief Sir Richard Branson said: "Our second spaceship is being built and tested by our wholly-owned sister organisation, The Spaceship Company, and together we are making any modifications or improvements that we feel are necessary to improve the safety of the vehicle.
"The spaceship is being worked on and will be operated by a strong team of stand-out professionals who are committed to helping us persevere and ultimately succeed."
He added that construction of a third space plane was also due to begin in 2015.
Virgin Galactic chief executive George Whitesides said: "We begin 2015 inspired by the words of support we have received from around the world, thankful for our global community of Future Astronauts (Virgin's astronaut corps) who have been so steadfast in their commitment, and proud of our team of over 400 rocket scientists, engineers, designers, and more who have come together to create the world's first commercial spaceline
"Most of all, we remain committed to the goal of opening space to all. 2015 will be an important and exciting year, and we are looking forward to the future."
The original rocket plane broke apart in the air after being released from a carrier jet some 50,000ft over California's Mojave desert.
Co-pilot Michael Alsbury was killed in the crash. The other pilot, Peter Siebold, escaped with minor injuries after being blown free and parachuting to the ground.
The crash is believed to have involved premature deployment of braking fins that are normally used to aid a safe descent.