Virgin Galactic says its SpaceShipTwo broke the sound barrier over California, a milestone in the company's drive to operate the first commercial space liner.

The rocket plane reached Mach 1.43 in the skies above the Mojave Desert Thursday, the second time the aircraft has broken the sound barrier, the Los Angeles Times reported.

SpaceShipTwo was taken to an altitude of about 46,000 feet by a carrier aircraft, and then released. After a short free fall, the ship fired its hybrid rocket motor -- powered by nitrous oxide and a rubber compound -- for 20 seconds.

With pilot Mark Stucky and co-pilot Clint Nichols aboard, it reached 56,000 feet in altitude, and then landed in Mojave after a 30-minute flight.

"This is a giant step," British billionaire and Virgin Galactic founder Richard Branson wrote in a blog post "Our spaceship is now the highest commercial winged vehicle in history!"

SpaceShipTwo is designed to be the world's first commercial space liner, making several trips a day carrying passengers paying $250,000 each into space for a brief journey during which they will experience weightlessness and observe the curvature of Earth.