China’s first home-grown and largest amphibious plane successfully made its first trial at sea on Sunday, state media reported, a major step towards final production. Kunlong, the prototype of the AG600 amphibious aircraft, took off from an airport in the east of the country in Rizhao, Shandong province, and headed to waters near Tuan Island in Qingdao. The plane skied for four minutes on the sea surface before taking off again to head back to Rizhao, according to state news agency Xinhua. The trial was declared a success and another major milestone since the plane first completed water-taxiing trials on a reservoir in Hubei province two years ago. Get the latest insights and analysis from our Global Impact newsletter on the big stories originating in China. “The successful sea trial marks another crucial step in the development of the project,” said Luo Ronghuai, general manager of the Aviation Industry Corporation of China. The sea trial was essential for production of the plane to move forward, said captain Zhao Sheng. “The plane needs experience and data in handling take-off and landing at sea as the maritime environment – wind, currents, waves, temperature and a corrosive environment – is totally different from lakes,” Zhao said. The project had been suspended for over a month because of the Covid-19 outbreak in Hubei, where the first infections were reported, and the prototype plane was at risk of being damaged without adequate maintenance, state broadcaster CCTV reported in April. The Aviation Industry Corporation of China sent a reinforcement team to Hubei in mid-March during lockdown in the province, to resume preparations for further tests of the plane. Once manufactured, the AG600 will fill in a gap in China’s forest firefighting, maritime search-and-rescue and natural disaster relief activities. Roughly the size of a Boeing 737 – at 37 metres (120 feet) long with a 38.8-metre wingspan – it has a range of up to 4,500km (2,800 miles). The aircraft can carry out sea-rescue operations under complex meteorological conditions and can take off and land in 2-metre-high waves. It can transport 50 people during a maritime search-and-rescue mission. It will also support China’s marine monitoring and safety patrols. The AG600 is bigger and has a greater take-off weight than Japan’s US-2, the world’s most advanced amphibious plane. If deployed in the southern island province of Hainan, the aircraft could reach anywhere in the South China Sea within four hours. It could also serve as a cargo or passenger carrier between the Chinese-controlled islands in the region. The developers have been building four prototypes. If tests go well, the amphibious aircraft is expected to be finalised and delivered by 2022, Xinhua reported.