A private spaceship being developed for space tourism by Virgin Galactic crashed Friday during a test flight over California's Mojave Desert, killing one of two pilots. In the second crash of a private commercial spacecraft this week, Virgin Galactic's SpaceShipTwo burned and broke into pieces. The company said the accident happened during a powered test flight and resulted in the loss of the aircraft, dpa reported. The flight was being conducted to test an engine and a new fuel mixture, said Kevin Mickey, president of Virgin Galactic's partner Scaled Composites. "We were flying a rocket motor today that had been thoroughly tested on the ground - we expected no anomalies with this motor today," Mickey said at a news conference. The new fuel formulation had "been tested on the ground, many times," Mickey said. Stuart Witt, chief executive and general manager of the Mojave Air and Spaceport, said he detected nothing abnormal in the flight and only became concerned when he didn't hear anything. The Federal Aviation Administration (FAA) and the National Transportation Safety Board are investigating the crash.