A previous SITREP chronicles some of the growing tension of the Japanese held/Chinese claimed  Senkaku Islands.  China’s claim of a new “air defense zone over the islands initiated a US response of flying B52s through it as well as joint Japanese-US naval exercises.  The Chinese responded with launching their one carrier on an “exercise” and repeated incidents of Japanese and S. Korean aircraft ignoring the zone have caused the Chinese to escalate by sending fighters to “patrol” the zone.  Not likely, but putting military aircraft in the same airspace poses a probability of an incident like the 2001 incident when a Chinese fighter clipped a US reconnaissance flight.  The Chinese pilot was killed and the US spy plane had to land in China where the Chinese took the plane apart.