The South China Sea is claimed by China, but those claims are contested by the Philippines, Vietnam, Malaysia, Taiwan and Brunei. The Navy explained that the patrol was just a part of the beginning "routine operations." According to the U.S. Defense Department, about 30 percent of global trade goes through the South China Sea, equaling about $5.3 trillion dollars. The sea is also the home to plentiful fishing, natural gas and oil reserves.
Last week, the spokesman for China's Foreign Ministry spoke out against the news of the patrol.
China has indisputable sovereignty over the South China Sea islands and their adjacent waters ... China respects and upholds the freedom of navigation and overflight in the South China Sea which countries enjoy under international law, but firmly opposes any country's attempt to undermine China's sovereignty and security in the name of the freedom of navigation and overflight.
He also asked the United States to "refrain from challenging China's sovereignty and security" in the South China Sea. China has also been creating islands in the sea and arming them with weapons and military-level airfields.
This isn't the United States' first time in the sea. Most recently, a Navy patrol plane and a Chinese surveillance plane flew just a thousand feet from each other in the waters.