China has imposed a 40-day offshore airspace restriction larger than Taiwan without explanation, signaling a potential shift toward sustained military readiness near Japan and U.S. allies.
China filed Notices to Air Missions (NOTAMs) reserving offshore airspace in the Yellow Sea and East China Sea from March 27 to May 6, a 40-day window, without announcing any military exercises or offering a public explanation. The reserved zones cover an area larger than Taiwan’s main island, spanning from the Yellow Sea facing South Korea to the East China Sea facing Japan, including airspace north and south of Shanghai.
The restrictions carry no vertical ceiling, designated SFC-UNL, meaning surface to unlimited altitude. Civil aviation remains unaffected. Commercial flights are still permitted to pass through these areas, but must coordinate carefully with Chinese air traffic control authorities.
NOTAMs of this type have previously been used to signal Chinese military exercises, which typically last a few days. China has issued comparable restrictions along the same coastline at least four times in the past 18 months, but those lasted only three days and were openly linked to announced exercises, missile launches, or live-fire training events.
This time, Beijing provided no warning, no declared exercise, and no explanation. China’s Ministry of Defense and civil aviation authorities issued no statements and did not respond to requests for comment.
The November and December 2024 precedent is directly relevant. In November 2024, Shanghai air traffic control issued a NOTAM restricting seven large sections of airspace off China’s coast for periods spanning three days. Those zones overlapped with airspace subsequently used during large-scale military exercises in December 2024.
China provided no reason for the November restrictions, and they passed relatively unnoticed by the international media. Analysts assessed that they may have served as a rehearsal for the more significant airspace reservations that accompanied the December exercises.
Ray Powell, director of Stanford University’s SeaLight project, which tracks Chinese maritime activity, told The Wall Street Journal that the combination of SFC-UNL designation and a 40-day duration with no announced exercise suggests “a sustained operational readiness posture—and one that China apparently doesn’t feel the need to explain.”
Christopher Sharman, director of the U.S. Naval War College’s China Maritime Studies Institute, said the zones could provide China an opportunity to practice air combat maneuvers relevant to a Taiwan contingency.
Ben Lewis of PLATracker, an organization that analyzes the Chinese military and regional security development, assessed that the longer window likely gives China’s military scheduling flexibility for spring training and said he does not anticipate major exercises given the Kuomintang chair’s visit to Beijing and the planned Trump–Xi summit in mid-May.
The restricted zones lie hundreds of miles north of Taiwan but sit directly along approaches facing Japan and South Korea. A senior Taiwanese security official told the Journal the reservation is “clearly aimed at Japan,” reflecting Chinese efforts to deter U.S. allies and erode American military influence in the Indo-Pacific while U.S. attention remains on the Middle East conflict.
Past Chinese drills have focused on controlling air routes the U.S. military would use in a Taiwan contingency, and the pause in daily PLA flights near Taiwan that preceded these NOTAMs also remains unexplained.
The restrictions carry implications for the United States, Japan, and Taiwan. The United States recently moved long-range missile assets from the Pacific to the Middle East, and the restricted zones cover approaches directly relevant to the U.S. Indo-Pacific Command force projection. Japan faces the most direct exposure, as the East China Sea portion of the restricted airspace faces Japan’s southwestern island chain, where Japan has deployed long-range missiles capable of reaching parts of mainland China.
By using a routine aviation mechanism without stating a military purpose, China imposes costs, heightened readiness, intelligence resources, and diplomatic caution on all three parties simultaneously, without triggering the international backlash that an announced large-scale exercise would generate.
No public U.S. government response to the restrictions has been reported. The U.S. military nonetheless continues operations in the region. USS John Finn conducted a Taiwan Strait transit on March 10, with the U.S. 7th Fleet stating the mission “demonstrates the U.S. commitment to a free and open Indo-Pacific” and that American forces “will continue to fly, sail, and operate anywhere international law allows.”
On March 28, one day after China’s airspace restrictions took effect, Japanese fighter jets scrambled to intercept a new variant of China’s Y-9FQ anti-submarine warfare aircraft over the East China Sea, approximately 160 miles northeast of Okinawa. Japan’s Ministry of Defense, in releasing details of the intercept, stated that it “will continue to collect information and conduct surveillance on military movements around Japan 24 hours a day and will take all necessary measures against airspace violations.”
Japan has also increased defense spending to 2 percent of GDP ahead of schedule and is working with the United States to expand the joint military presence in Japan’s southwestern region.
