Japan's Self Defense Forces on Thursday said the air force conducted 91 scrambles against Chinese aircraft in the three-month period, the largest quarterly tally since Tokyo started disclosing such data in 2005. For decades, Japan has routinely dispatched fighter jets to keep foreign aircraft—mostly Russian jets—out of its airspace, but the rising number of scrambles against Chinese planes is relatively new.
During the first three quarters of the year that ends in March, Japan conducted 160 scrambles against Chinese planes, compared with 156 in the year ended March 2012, and 54 in the prior year. The latest quarterly number was up from 54 scrambles for the July-September period and 15 for April-June.
Diplomatic dialogue between the two nations aimed at resolving the dispute has been largely put on hold following a Chinese leadership change in November and a Japanese one in December.
In a subtle initial effort by Japan's new government to reach out to China, the leader of a small party in the ruling coalition is visiting Beijing this week, carrying a letter from Prime Minister Shinzo Abe to Xi Jingping, China's new leader.
Natsuo Yamaguchi, the leader of the New Komeito party, met with Chinese foreign minister Yang Jienchi Thursday.
"You come to China for the visit at an important time of Sino-Japanese relationship," Mr. Yang told Mr. Yamaguchi, China's state-run Xinhua news agency reported. "We hope the tour contributes to maintaining and pushing forward the ties."
The content of Mr. Abe's letter hasn't been disclosed.
Until recently, the confrontation over the disputed islands centered on cat-and-mouse chases between lightly armed coast-guard cutters from the two sides.
Government officials and analysts, however, have expressed concerns that the dispute may have entered into a new and riskier stage with more frequent appearances of Chinese naval ships and aircraft from both nations in the areas increasingly close to the islands.
James Schoff, an analyst at Carnegie Endowment for International Peace, said what is new is the "frequency and the duration of lingering and loitering" by Chinese patrol boats in sensitive waters and the use of aircraft over the disputed islands.
"It fits into the Chinese narrative that we are there to keep you out," said Mr. Schoff, who was until recently an Asia policy adviser to the U.S. secretary of defense. "The narrative has changed to be 'Not only is it we can go there but you can't be here.' That's a fundamental change."
In a move that alarmed officials from Tokyo and Washington, a patrol plane from China's State Oceanic Administration flew into the airspace above the disputed islands on Dec. 13, undetected by Japanese military radar. Once a coast-guard boat spotted it, the Japanese air force scrambled eight F-15 fighter jets.
Taking the confrontation one step further, China's defense ministry said on Jan. 11 that Beijing sent in two of its J-10 fighters close to the airspace over the islands after a Chinese plane was followed by Japanese F-15 fighters, Xinhua reported.
To rein in tensions, U.S. Secretary of State Hillary Clinton last Friday called on Beijing and Tokyo "to take steps to prevent incidents and manage disagreement through peaceful means" while warning Beijing that the U.S. "oppose any unilateral action that would seek to undermine Japanese administration."
China snapped back. On Sunday, Chinese foreign ministry spokesman Qin Gang said "the comments by the U.S. side are ignorant of facts and indiscriminate of rights and wrongs. China has long contested Japan's effective control of the islands and blames the U.S. for placing the rocky outcrops under the control of Japan after World War II."