A ship-borne helicopter attached to the guided-missile frigate Yancheng (546) of the PLA Navy hovers in the air to conduct search-and-rescue operation during the China-U.S. joint maritime training in the waters near San Diego on Dec. 9. A Chinese naval fleet comprised of the guided-missile frigate Yancheng (546), the guided-missile frigate Daqing (576) and the comprehensive supply ship Taihu (889) concluded a four-day friendly visit to San Diego, on Dec. 9, 2016. (Photo/cnr.cn)