US Indo-Pacific Command (USINDOPACOM) Thursday said in a statement that on December 21, a Chinese Navy aircraft came within 20 feet of a US Air Force RC-135 surveillance plane conducting routine operations in the South China Sea, forcing the RC-135 to take evasive maneuvers to avoid a collision.USINDOPACOM called the event an “unsafe maneuver” by the Chinese aircraft, attaching video evidence of the incident. It further added:The U.S. Indo-Pacific Joint Force is dedicated to a free and open Indo-Pacific region and will continue to fly, sail and operate at sea and in international airspace with due regard for the safety of all vessels and aircraft under international law. We expect all countries in the Indo-Pacific region to use international airspace safely and in accordance with international law.The South China Sea is of great economic and strategic importance to countries bordering it. Trade worth $3.37 trillion passes through it. It is rich in oil and natural gas reserves, besides being an important fishing ground for regional fisheries.The region is subject to numerous sovereignty claims by China, Brunei, Malaysia, the Philippines, Taiwan, and Vietnam. China has the largest sovereignty claim out of all countries party to the dispute. Its claims are defined by the nine-dash line based on the 1958 “Declaration of the Government of the People’s Republic of China on China’s Territorial Sea.”The US and its allies routinely conduct surveillance and freedom-of-navigation operations in the South China Sea to test Chinese territorial claims. This has become a point of contention in US-China relations.In May, the Australian Department of Defence reported that a Chinese fighter jet had intercepted an Australian Air Force P-8 aircraft conducting routine maritime surveillance operations in a “dangerous maneuver” which posed a “safety threat to the P-8 aircraft and its crew.”In January, the Chinese military said it tracked and issued a warning to a US warship, the USS Benfold which entered its disputed territorial waters.