The space agency announced that the flights, at Moffett Field, Calif., are sold out, but more flights will be scheduled for later this year. The flights are a result of an agreement between NASA and Zero Gravity, of Las Vegas.

A Reimbursable Space Act Agreement between NASA's Ames and Zero-G allows the company to use the airfield while conducting its flights. At also forms the basis for research cooperation between NASA and Zero-G, scheduled to begin this fall.

The company will use a modified Boeing 727-200 aircraft, called G-Force One, with passengers aboard on Saturday. The passengers will feel the same weightlessness that astronauts experience while orbiting the Earth and the same gravity conditions they would encounter on the moon and Mars. The weightlessness will last for brief periods during the flight.

Peter H. Diamandis, chairman of Zero-G, which recently received a NASA contract to research astronaut training, said passengers will be able to "fly like Superman and float in midair just like NASA astronauts from an actual NASA center."

The Boeing 727-200 is one of the quietest aircrafts in service, NASA said. Zero-G said the flights will occur during daylight hours and not interfere with its operations. The company will reimburse NASA for runway and support costs.

Zero-G began offering weightless flights to the public in June 2006, from NASA's Kennedy Space Center in Florida. The company operated up to seven flights per week, up to a maximum of 280 flights a year in Florida.

Ames director S. Pete Worden said the cooperative agreement between NASA and Zero-G will enhance the space agency's partnerships with the growing commercial space industry.