The five-year countdown has started for the launch of a revolutionary privately-funded space travel service involving the world's largest aircraft. Stratolaunch Systems, headed by philanthropist and businessman Paul G Allen and aerospace leader Burt Rutan, is the American company behind the air-launch space travel.

The Alabama-based company will initially undertake government and commercial freight projects, but it is later hoping to take humans into space.

Paul G Allen, who was previously behind the SpaceShipOne manned rocket, says, "I have long dreamed about taking the next big step in private space flight after the success of SpaceShipOne - to offer a flexible, orbital space delivery system.

"We are at the dawn of radical change in the space launch industry. Stratolaunch Systems is pioneering an innovative solution that will revolutionise space travel."

The space ship will consist of three elements:

· The largest carrier aircraft in the world will be developed by Scaled Composites, founded by Burt Rutan

· A multi-stage booster constructed by Space Exploration Technologies

· An ultra-modern mating and integration system, enabling a booster of up to 490,000 pounds to be carried. It will be constructed by aerospace engineering company, Dynetics.

Air launches have several advantages over ground launches, including greater safety, flexibility, rapid turnaround and lower costs, Stratolaunch Systems claim.

Burt Rutan says, "Paul and I pioneered private space travel with SpaceShipOne, which led to Virgin Galactic's commercial suborbital SpaceShipTwo Program.

Now, we will have the opportunity to extend that capability to orbit and beyond. Paul has proven himself a visionary with the will, commitment and courage to continue pushing the boundaries of space technology.

"We are well aware of the challenges ahead, but we have put together an incredible research team that will draw inspiration from Paul's vision."

Stratolaunch Systems' CEO and President, Gary Wentz, a former NASA chief engineer, says the new service will transform space travel.

Stratolaunch board member Mike Griffin, an ex-NASA administrator, says, "We believe this technology has the potential to someday make space flight routine by removing many of the constraints associated with ground launched rockets.

"Our system will also provide the flexibility to launch from a large variety of locations."

After conducting unmanned space flights of up to 1,300 nautical miles to the payload launching point, it will seek to offer low-orbit flights for humans.

The flights will be launched from a spaceport, such as the Kennedy Space Centre, or big airports. The launch aircraft will employ six 747 jet engines, weigh over 1.2 million pounds, possess a wingspan of over 380 feet and need a 12,000-foot runway. Computer systems onboard will control the countdown and booster firing.

The spacecraft will be constructed in a hanger shortly to be built at Mojave Air and Space Port, near where SpaceShipOne was built by Scale Composites and went to complete three successful sub-orbital flights.

Scaled Composites President Doug Shane says, "Scaled is all about achieving milestones and pursuing breakthroughs, and this project offers both - building the largest airplane in the world, and achieving the manufacturing breakthroughs that will enable Scaled to accomplish it. We are thrilled to be a part of this development program.

"We anticipate significant hiring of engineering, manufacturing, and support staff in the near and medium term."

Space Exploration Technologies, of California, will build the multi-stage booster. Its President, Gwynne Shotwell, says, "Paul Allen and Burt Rutan helped generate enormous interest in space with White Knight and SpaceShipOne,

"There was no way we weren't going to be involved in their next great endeavour. We are very excited."

The mating and integration system, test and operational support and systems engineering is coming from Dynetics.

Vice President and Stratolaunch Board Member, David King, says, "We are excited to play such a major role on this system. This is an ambitious project unlike any that has been undertaken and I am confident the Stratolaunch team has the experience and capabilities to accomplish the mission."

Paul Allen hinted at the pioneering project in his book, Idea Man, saying he was "considering a new initiative with that magical contraption I never wearied of sketching as a boy: the rocket ship."