In 2001, air force Predator drones flew 7,500 hours. By the close of last year, that number topped 70,000. As the tempo of robotic air operations has steadily increased, crashes have, not surprisingly, become more frequent. In 2001, just two drones were destroyed in accidents. In 2008, eight drones fell from the sky. Last year, the number reached 13. (Accident rates are, however, dropping according to an air force report relying on figures from 2009.)