Chinese officials issued a radio warning to an American B1-B Lancer Bomber flying near South Korea on Sunday, claiming that the aircraft had illegally entered Chinese airspace and ordering them to leave.

The airspace in question is included in China’s Air Defense Identification Zone (ADIZ) over the East China Sea, a territory China officially claimed in 2013, but that America and its allies continue to identify as international airspace.  The particular region of the East China Sea the B1-B was flying over includes a chain of islands that has seen overlapping territorial claims levied by the Chinese, Japanese, and South Koreans.

According to China’s official policy, aircraft must notify China before entering into the contested region – a policy both American and Japanese aircraft do not recognize or honor.

“Pacific Air Forces … did not recognize the Chinese Air Defense Identification Zone (ADIZ) when it was announced in November of 2013, and does not recognize it today,” US Pacific Air Forces spokesman Major Phil Ventura told reporters.  “The ADIZ has not changed our operations.”

The American B1-B Bomber did not deviate from its flight path upon receiving the Chinese warning, but did respond to their air traffic controllers, stating that they were conducting routine operations in international airspace and would not be deterred.  The Chinese military did not dispatch any aircraft to intercept the bomber.

China’s claim to the airspace was opposed at its very inception in 2013 by Washington and Tokyo alike, and conflicting reports since have indicated that even China’s enforcement of policy within the ADIZ has been sporadic and inconsistent.  The island chain in question, which China refers to as the Diaoyu Islands and America’s allies call the Senkaku Islands, have been the site of multiple face-offs between Chinese and Japanese forces, but none have ever resulted in anything more than posturing.

The United States and South Korea are currently amid annual military exercises along South Korea’s northern border, which has seen air operations conducted by U.S., Japanese, and South Korean aircraft throughout the region.  A subsequent B1-B Lancer Bomber flight was conducted on Tuesday in the same region, this time with Japan Air Self Defense Force F-15J Eagles, South Korean Air Force F-15K Slam Eagles, and F-16 Fighting Falcons participating as well.

The jets conducted a series of intercept and formation training drills intended to “foster increased interoperability between Japanese and U.S. aircraft.”