“I want to stress that these activities are completely normal. The Diaoyu and its affiliated islands are China’s inherent territory since ancient times,” Chinese Foreign Ministry spokesman Hong Lei said of the plane. “China requires the Japanese side stop illegal activities in the waters and airspace of the Diaoyu islands.”
Osamu Fujimura, Japan's chief cabinet secretary, called the Chinese move “extremely regrettable.”
International law forbids entering another nation's airspace without permission and gives countries the right to expel unauthorized aircraft with force immediately. In contrast, foreign ships are able sail through a nation's territorial waters as long as it is considered "innocent passage."
The incident also puts further pressure on [Prime Minister Yoshihiko Noda], whose ruling Democratic Party of Japan is likely to face a decisive defeat in Sunday's elections, according to various national polls. Shinzo Abe, who's likely to take his job away, has criticized Mr. Noda for his handling of the territorial issues, and called for a confrontational approach focused on the use of "physical power," rather than diplomacy.