The US may not be the only country to have dipped a toe in China's newly declared air defense zone: Japan and South Korea now say they've both flown planes through it, unannounced, as well. A rep for the Japan government describes its activity as routine "surveillance" over the the East China Sea, though he did not specify when the flight occurred. Since Saturday, "we have continued our surveillance activities as before in the East China Sea, including in the zone," he said. South Korea says it entered the zone the same day the US did: Tuesday.
Per China's Saturday declaration of the zone, any planes entering the airspace must convey a flight plan to China and accept its instructions, or else be subject to emergency military measures, reports the BBC (which has a great graphic outlining the area's air zones). Japan and South Korea did no such thing, seemingly without response. The countries are embroiled in a battle with China over bits of land contained in the zone: islands alternately known as the Senkaku and Diaoyu that Japan claims, as well as a submerged rock that South Korea considers part of its land. Meanwhile, the AP reports that the Philippines today joined the clamor against the zone, with a government rep saying the zone infringes on the freedom to fly in international airspace and compromises the safety of civil aviation.