Commercial aviation began within a decade of the Wright Brothers' 1903 flight at Kitty Hawk. Yet 43 years after Yuri Gagarin's first manned spaceflight, you still can't book a seat on a regularly scheduled spaceship.

	Scaled Composites via AP SpaceShipOne comes in for a landing at the Mojave Civilian Aerospace Test Center in California in this undated photo. Click photo for larger image.

Weather and technology permitting, the era of commercial manned spaceflight finally may open a week from today, when the first privately developed rocket plane is scheduled to launch into history.

Funded by Paul G. Allen, billionaire co-founder of Microsoft Corp., and designed by aviation genius Burt Rutan, "SpaceShipOne" will attempt the first non-government manned flight to exit Earth's atmosphere.

After riding to an altitude of 50,000 feet on a carrier aircraft named the White Knight, SpaceShipOne and its pilot will drop loose. An 80-second blast from a rocket motor will lift the small ship to an altitude of 62 miles, well beyond the 50-mile mark that the U.S. Air Force terms "worthy of astronaut wings."

The pilot will become the world's first astronaut coined in a privately funded program. He then will guide SpaceShipOne to a landing in California's Mojave Desert, where organizers expect TV cameras and thousands of spectators.

"SpaceShipOne already has some impressive successes on the way to space, and I think it has a good chance of making it the rest of the way," said Dr. Marc Rayman, director of NASA's DeepSpace 1 mission, which successfully tested a new spacecraft propulsion system and other technologies. "I wish them the best for a successful trip."

SpaceShipOne will fly for the same reason that Charles Lindbergh crossed the Atlantic in 1927 -- glory and cash.

Lindbergh won the $25,000 Orteig Prize for his historic achievement. Hundreds of similar prizes offered between 1905 and 1935 spurred innovations in aircraft design, accelerating the development of commercial aviation, noted Peter H. Diamandis in an interview.

Diamandis is chairman and president of the X Prize Foundation, which has offered $10 million to the first private group that launches a person into space in hopes of eventually making spaceflight accessible to the general public on a regular basis at a reasonable cost.

More than 20 groups are competing for the X Prize, but thanks to Paul Allen's money and Burt Rutan's genius, SpaceShipOne is far and away the No. 1 competitor.

Rutan designed the Voyager, which in 1986 made the first nonstop flight around the world without stopping for refueling. A team at his company, Scaled Composites LLC, worked in secret for two years to build SpaceShipOne.

Allen has been an investor and philanthropist since leaving Microsoft in 1983. He has funded other space-related projects, including a telescope complex being built in California to search for intelligence life elsewhere in the universe.

SpaceShipOne has passed more than a dozen shakeout tests, including glides and rocket-powered flights. The most recent, flown by veteran test pilot Mike Melvill, 62, reached an altitude of almost 38 miles in April.

SpaceShipOne embraces the tried-and-true approach pioneered in the 1950s by the fabled military X-15 program. The X-15 was a rocket plane, which a giant B-52 bomber released at high altitudes. Pilots flew different versions of the X-15 to more than 65 miles high.

Other X Prize entrants are in earlier stages of development. They include vertical take-off rockets, space planes that would take off and land on a runway, and X-15-type vehicles lofted by carrier planes or helium balloons. Rayman said several of the designs might ultimately be successful.

"There are many examples throughout history of private investors following the government into new frontiers, and I think it's extremely exciting that we are on the verge of seeing this happen with space travel," Rayman said.

Among them are Earth-orbiting communications satellites, which now account for a large fraction of all space launches.

Historians disagree on exactly when the first airplane passenger service began in the United States. By 1913, however, a regularly scheduled hydroplane was carrying passengers between San Francisco and Oakland, Calif., harbors.

Diamandis envisions the X Prize fostering the rapid emergence of a space tourism industry with annual sales that could top $2.3 billion by 2020. Market forecasts suggest 500 people a year might pay $100,000 for suborbital flights -- officially making them astronauts -- once they get the chance, with annual ticket sales rising to 13,000 by 2020.

The current X Prize may lead to another for development of a commercially feasible vehicle for orbital flights. Tickets on orbital flights might fetch $1 million to $20 million.

Rayman noted that space tourism already is a reality for the very rich. U.S. businessman Dennis Tito paid the Russians a reported $20 million for an eight-day stay on the International Space Station in 2001. Russia's Energiya space corporation is seeking investors to help build Mini Station 1, the first commercial orbital station designed for space tourists.

If the market is so attractive, why haven't the big aircraft companies jumped in and built a commercial passenger spaceship?

"The answer is not what people typically expect," Diamandis said. "A colleague of mine who is a Boeing executive explained the situation bluntly, 'Why should we take the risk? If some entrepreneurial X Prize team succeeds in building a working spaceship and proving the marketplace exists, we'll just buy that company.' "

SpaceShipOne will not win the X Prize with a successful flight on June 21. Contest rules require that it would have to fly again within two weeks, carrying weight equivalent to two passengers. Diamandis said the requirement helps to assure that a space plane is commercially feasible and does not need extensive repairs after each flight.

"As a lifelong space enthusiast, I'd love to take a trip away from Earth," Rayman noted. "After all, everyone likes to leave home now and then."

So how about taking that second flight of SpaceShipOne?

"I don't think so," he replied.

"I would love to travel into space, but I am not willing to take a large risk to do so. So before taking such a flight, I would want to have a history of successes behind the machine that propels me into an unforgiving environment and hurtles back to the very solid Earth."

For more information on the X Prize and the teams competing to win it, visit www.xprize.org.