Virgin Galactic will continue work on 2nd rocket plane despite crash Virgin Galactic's chief executive said Sunday that the company is planning to finish work on a second rocket plane by year's end, despite the fatal crash of the SpaceShipTwo. George Whitesides said the company is working closely with investigators from the National Transportation Safety Board to determine what caused the rocket plane to break apart in mid-air on Friday morning, killing one pilot and seriously injuring another. "The second spaceship is very advanced in its construction," he said. We need to work closely with the NTSB ... to work out as rapidly as we can what happened, and then to move forward. We're hopeful we can make rapid progress. Christopher Hart, the NTSB's acting chairman, said Saturday that the investigation of the crash site in the desert about 20 miles northeast of Mojave would take a few more days. A final report could take as long as a year, he said. Friday's test flight of SpaceShipTwo was the first time it was to fly by firing a new rocket motor using a plastic-based fuel - leading to speculation that the engine may have been a factor in the crash. Until May, SpaceShipTwo had used a different motor that burned a rubber-based fuel. Whitesides said he couldn't talk about the accident during the investigation. When asked if the company would continue testing the new engine on the ground, he said, "I think the short answer is "yes."" The engine had passed ground tests before Friday's flight that satisfied engineers who determined it was "qualified" to be tested in flight. That process, he said, involved "a small number of firings in a row to make sure you get the same result." "We have qualified the engine that we were putting into flight tests," he said. I'm sure that we will continue that work. He added, "As we've always said, we expect to continue to improve all our systems as time goes on just like any manufacturer would." He said Virgin Galactic had spent $500 million so far in its quest to fly tourists into space. The company had insurance, he said, that would help cover the cost of Friday's crash. Test pilot Michael Alsbury, 39, died in the crash. His body was found near the fuselage of the main wreckage, authorities said. Surviving pilot Peter Siebold, 43, suffered a shoulder injury and was "alert and talking with his family and doctors" on Saturday, according to Scaled Composites, the company that designed SpaceShipTwo. Twitter: @MelodyPetersen