Asiana Airlines does not believe that the fatal crash of one of its Boeing 777 planes in San Francisco on Saturday was caused by mechanical failure, although it refused to be drawn on whether the fault lay with pilot error. "For now, we acknowledge that there were no problems caused by the 777-200 plane or (its) engines," Yoon Young-doo, the president and CEO of the airline, told a media conference on Sunday at the company headquarters, according to a report of Reuters.