The territorial dispute with Beijing over the South China Sea remains a security challenge despite an improvement in bilateral ties, the Philippines defense chief said on Monday. Delfin Lorenzana made the comment at a naval base south of the capital Manila as he accepted three maritime surveillance planes from Japan, Reuters reports. The Japanese donated second-hand TC90 planes will boost the navy’s capability to gather intelligence in the disputed South China Sea, according to Lorenzana. “We must admit that much still has to be done to boost our military capability equipment in order to meet a number of persistent maritime security challenges,” he said, referring to territorial disputes with China and other countries over resource-rich areas in the South China Sea. China claims almost the entire South China Sea, where about $5 trillion worth of sea-borne goods pass every year.