China’s domestically developed AG600, the world’s largest amphibious aircraft, performed its maiden flight on Sunday from an airport on the shores of the South China Sea, the latest step in a military modernisation programme. China has stepped up research on advanced military equipment as it adopts a more muscular approach to territorial disputes in places such as the disputed South China Sea, rattling nerves in the Asia-Pacific region and the United States. State television showed live images of the AG600 lifting off from Zhuhai airport in the southern province of Guangdong, which sits on the South China Sea coast. It...