Scaled Composites, the aerospace company run by legendary designer Burt Rutan, announced Wednesday that it will attempt the first manned suborbital flight of its SpaceShipOne vehicle on June 21.

In a statement released Wednesday morning the company announced the SpaceShipOne is scheduled to fly to an altitude of 100 kilometers - the widely-accepted boundary of space - on the morning of June 21, on a flight that will take off and land from Mojave Airport in California.

SpaceShipOne has performed three powered test flights, on December 17 of last year and on April 8 and May 13 of this year. On the May 13 flight SpaceShipOne reached a peak altitude of over 64 kilometers, leading to speculation that the next flight would shoot for 100 km.

SpaceShipOne, developed by Scaled Composites with funding provided by billionaire Paul Allen, is a small winged vehicle capable of carrying three people. It is carried aloft underneath a specially-designed carrier aircraft called White Knight. At an altitude of about 15,000 meters SpaceShipOne is released from White Knight and fires a hybrid-propellant rocket engine. The engine burn, 80 seconds long for the full-scale mission, propels SpaceShipOne on a suborbital trajectory.

During the descending phase of the flight, with the vehicle reaching speeds in excess of Mach 3, SpaceShipOne raises its tail section to put it into a more stable configuration before lowering it again. The vehicle then glides to a landing at the same airport where it took off.

"Since Yuri Gagarin and Al Shepard's epic flights in 1961, all space missions have been flown only under large, expensive government efforts. By contrast, our program involves a few, dedicated individuals who are focused entirely on making spaceflight affordable," said Rutan. "Without the entrepreneur approach, space access would continue to be out of reach for ordinary citizens. The SpaceShipOne flights will change all that and encourage others to usher in a new, low-cost era in space travel."

"Every time SpaceShipOne flies we demonstrate that relatively modest amounts of private funding can significantly increase the boundaries of commercial space technology," said Allen, best known as the co-founder of Microsoft. "Burt Rutan and his team at Scaled Composites have accomplished amazing things by conducting the first mission of this kind without any government backing."

SpaceShipOne is a leading contender to win the $10-million Ansari X Prize for the first privately-developed suborbital reusable vehicle able to carry three people to 100 km twice within two weeks. The June 21 flight will not be one of the two qualification flights for the prize, as the vehicle will not carry the additional passengers, or their equivalent mass, as required by the rules. According to the Scaled statement, "Based on the success of the June space flight attempt, SpaceShipOne will later compete for the Ansari X Prize."

Wednesday's announcement was an unusual revelation from the company. Scaled has conducted its previous test flights, including both the three previous powered flights as well as a series of unpowered glide tests, in secrecy, announcing the flights only after they took place. When the FAA's Office of Commercial Space Transportation issued Scaled a launch license for SpaceShipOne in April, it granted the company a waiver from a requirement to provide public notice for its launches, because such notice "may have the unintended effect of drawing spectators to the launch area thereby increasing risk to public safety and the safety of property."

Instead, the June 21 will be open to the public, and Scaled will be encouraging the public to attend. "Who is invited?" asks Scaled in a "frequently asked questions" document included with the release announcing the launch. "Everyone, especially children. They will want to tell their children that they were there to see the event that triggered the industry of private space tourism."