San Francisco, Sep 10 (IANS): Virgin Galactic has announced that it has successfully test-flown its new spaceship, two years after a pilot was killed in one of its flight tests.

The flight, which took off from and landed back at an air and space port in California on Friday, lasted nearly four hours over the Mojave desert while reaching a maximum altitude of around 15,000 metres, the spaceflight company said in a blog post.

"Today marks an exciting milestone in our shared quest to open space to change the world for good," Xinhua news agency reported citing the post as saying.

The test was a "captive carry", according to the company, as the SpaceshipTwo craft, or the VSS Unity, stayed attached to its carrier, WhiteKnightTwo aircraft, for the entire flight.

The six-passenger, two-pilot winged space plane has been designed to take passengers on five-minute voyages into suborbital space.

The flight was operated by four test pilots -- two in SpaceShipTwo and two were on the carrier.

The aim of the flight was to capture "high fidelity aerodynamic performance data" on the vehicle, while allowing the teams to gain further experience operating a crewed flight.

It has been two years since the original SpaceShipTwo was destroyed in 2014 during a deadly test flight that killed one of its two pilots and seriously injured the other.

"Our first flight test was an emotional and fulfilling moment for our hardworking team," Virgin Galactic said.

More test flights and analysis are planned before the spaceship starts to take passengers to space.