China Creates New Aviation Mystery With Offshore Warning Zones

TAIPEI -- China has taken the unusual step of reserving swaths of offshore airspace without explanation for a period of 40 days, issuing alerts similar to those used to warn aviation authorities of Chinese military exercises, which typically last no more than a few days. Beijing hasn't declared any exercises in the area, sparking a new aviation mystery following an unexplained pause in military flights around Taiwan. The airspace reserved in the current alerts is hundreds of miles away from the self-governing island. The alerts are in effect from March 27 through May 6, and haven't previously been reported. Formally known as "Notice to Air Missions," or Notams, such designations are intended to inform pilots and aviation authorities of temporary airspace hazards or restrictions. Civil aviation appears unaffected, though coordination is needed for aircraft to transit such areas. The reserved airspace has no vertical ceiling -- designated in the Notams as "SFC-UNL." "What makes this especially notable is the combination of SFC-UNL with an extraordinary 40-day duration -- and no announced exercise," said Ray Powell, director of the SeaLight project at Stanford University, which tracks Chinese maritime activity. "That suggests not a discrete exercise but a sustained operational readiness posture -- and one that China apparently doesn't feel the need to explain." If the zones are confirmed to be linked to exercises, the warnings "would represent a meaningful shift in how Beijing uses airspace control as a tool of military signaling," Powell said. China's Ministry of Defense and Civil Aviation authorities haven't issued statements about the Notams, which isn't unusual, and didn't respond to requests for comment. The zones reserved by China cover a total area larger than Taiwan's main island, including offshore airspace to the north and south of Shanghai, according to information available from the U.S. Federal Aviation Administration. They extend from the Yellow Sea facing South Korea, south to waters of the East China Sea facing Japan. Some past Chinese drills have focused on establishing control of routes that might be used by the U.S. military in a potential conflict over Taiwan. The reserved airspace could "provide an opportunity to practice the kinds of air combat maneuvers that would be required in such a scenario," said Christopher Sharman, director of the U.S. Naval War College's China Maritime Studies Institute. The Notams follow another recent mystery about China's military intentions, when its air force paused what had been near-daily military flights near Taiwan -- a lull that coincided with the beginning of the U.S.-Israeli attack on Iran. China subsequently resumed the military flights. Officials in Taiwan believe China is seizing an opportunity to increase its active military presence while U.S. attention is diverted by the conflict in the Middle East, a senior Taiwan security official said. The current reservation of zones is "clearly aimed at Japan," as China looks to deter U.S. allies and erode American military influence in the Indo-Pacific region, the official said. The developments come alongside several politically significant events for China. President Trump and Chinese leader Xi Jinping had been scheduled to meet in Beijing around April 1, a summit that has been pushed back to mid-May. Xi, meanwhile, has invited the leader of Taiwan's opposition Kuomintang, or KMT, for a visit to China that is set to begin on Tuesday and expected to culminate with a meeting with the Chinese leader in Beijing. The KMT supports friendly ties with Beijing, in contrast with Taiwan's ruling Democratic Progressive Party, which advocates building up Taiwan's defenses. In addition, a U.S. congressional delegation recently visited Taiwan, Japan and South Korea. In Taiwan, U.S. senators urged the island's legislature to promptly approve a large military budget to bolster the island's defenses with U.S. arms purchases. After the Trump administration approved $11 billion in arms sales for Taiwan, China's military held large-scale drills around Taiwan in late December, dubbing them "Justice Mission 2025" and describing them as "a stern warning to Taiwan independence separatists and external interference forces." Also this week, Japan deployed long-range missiles capable of reaching China's mainland as part of a military buildup on its strategic southwestern islands. China has issued comparable reserved-airspace Notams along the same stretch of coast at least four times in the past 18 months, but those were shorter -- typically 3-day blocks -- said Ben Lewis, whose research organization, PLATracker, documents Chinese military activity. The longer window likely means China's military is "giving itself scheduling flexibility" for spring training, he said. But the current political context could weigh against the possibility of large-scale Chinese military exercises, Lewis said. "Given the impending visits by [KMT Chair] Cheng Li-wun this week and President Trump next month," he said, "as of now I am not anticipating any major exercises or flare-ups."