BEIJING – China's prototype stealth fighter made its first-known test flight Tuesday, marking dramatic progress in the country's efforts to develop cutting-edge military technologies. The plane dubbed the J-20 flew for about 15 minutes over an airfield in the southwestern city of Chengdu where it was spotted carrying out runway tests last week, Kanwa Asian Defense magazine editor Andrei Chang said. Photos of the plane in flight and on the ground surrounded by men in civilian clothes and army overcoats were also posted on unofficial Chinese military websites. A J-10 fighter — China's last homegrown jet — flew behind it...