Two American B-52 bombers on a training mission flew right through China's newly expanded air defense zone on Monday. The air space in question happens to be over a portion of the East China Sea claimed by both China and Japan. The "long-planned" training exercise, announced by Pentagon officials on Tuesday, underlines that the U.S. still considers the air claimed by China to be an international space. The planes flew from and returned to the U.S. territory of Guam. 

On Saturday, China unilaterally decided that any non-Chinese planes entering the space over the East China Sea — and a disputed grouping of islands — must give Beijing a flight plan ahead of time, and maintain radio contact with the country while in that space. The punishment for not complying, China warned, could include “defensive emergency measures." In other words, China might shoot down the plane. 

The U.S. did not inform China of its Monday flight. Pentagon spokesperson Col. Steve Warren told the Wall Street Journal on Monday that the U.S. "will not in any way change how we conduct our operations as a result of the Chinese policy of establishing an ADIZ, an Air Defense Identification Zone," indicating that the U.S. was moving forward with the previously planned training mission. White House spokesman Josh Earnest called the establishment of the zone "counterproductive," and urged Japan and China to settle their differences over the islands through diplomacy. 

Among other things, China's new ADIZ substantially overlaps an earlier one established by Japan, as the Aviationist outlines. Both countries consider the airspace to be theirs, although Japan currently administers the islands in that territory. American officials aren't explicitly framing today's flight as a rebuke, but that's pretty much how everyone will read it, including China. Secretary of Defense Chuck Hagel condemned the expansion in a weekend statement"We view this development as a destabilizing attempt to alter the status quo in the region," Hagel said, adding, "this unilateral action increases the risk of misunderstanding and miscalculations.”