The United States and the People's Republic of China disagree on the legality of the overflights by U.S. naval aircraft of the area where the incident occurred. This part of the South China Sea comprises part of the PRC's exclusive economic zone based on the United Nations Convention on the Law of the Sea (UNCLOS) and the Chinese claim that the Paracel Islands belong to China. This claim has been persistently contested by Vietnam. The United States remains neutral in this dispute, but patrols the sea regularly with military ships and planes, under what it calls "freedom of navigation" operations. The PRC interprets the convention as allowing it to preclude other nations' military operations within this area, but the United States does not recognize China's claim over the Paracel Islands and maintains that the Convention grants free navigation for all countries' aircraft and ships, including military aircraft and ships, within a country's exclusive economic zone. Although the United States is not party to UNCLOS, it has accepted and complies with nearly all of the treaty's provisions.