TAIPEI (Taiwan News) — China has announced restricted airspace off its coast for 40 days without explaining the move, the Wall Street Journal reported.

The zones cover areas north and south of Shanghai, according to the US Federal Aviation Administration. They also extend from the Yellow Sea to the East China Sea. The restrictions run from March 27 to May 6.

Beijing has not announced any exercises in the area, the Journal said. The reserved airspace has no vertical ceiling, designated “SFC-UNL,” and is located hundreds of miles from Taiwan.

“What makes this especially notable is the combination of SFC-UNL with an extraordinary 40-day duration — and no announced exercise,” Ray Powell, director of the SeaLight project at Stanford University, told the Journal. “That suggests not a discrete exercise but a sustained operational readiness posture — and one that China apparently doesn’t feel the need to explain.”

Taiwan officials think China is boosting its regional military presence while the US is bogged down by the conflict with Iran, a top Taiwanese security official said.

The zones are “clearly aimed at Japan,” and are an attempt to deter and erode the US military in the region, the official said.

Christopher Sharman, director of the US Naval War College’s China Maritime Studies Institute, said the restricted airspace could “provide an opportunity to practice the kinds of air combat maneuvers that would be required in such a scenario.”

China paused its daily intrusions into Taiwan’s air defense identification zone from February to early March. A senior Taiwan security official said at the time that “Beijing might be trying to create a false impression" ahead of the planned meeting between US President Donald Trump and Chinese leader Xi Jinping. "I am peaceful, I am moving toward peace, so you should stop selling weapons to Taiwan,” they said.

This longer window suggests that China’s military is “giving itself scheduling flexibility” for spring training, Ben Lewis, who runs PLATracker, a platform that documents Chinese military activity, said. However, he said that “Given the impending visits by [KMT Chair] Cheng Li-wun (鄭麗文) this week and President Trump next month, as of now I am not anticipating any major exercises or flare-ups.”