China plans to block the airspace north of Taiwan from April 16 to 18, according to four individuals with knowledge of the situation, which may affect aircraft throughout the area.

The foreign ministries of China and Taiwan did not immediately reply to calls for comment.

Four officials outside China, speaking on the condition of anonymity owing to the delicacy of the situation, told Reuters that the block would disrupt Taiwan’s northern flight information region (FIR) and that they were unaware of the cause for the restrictions.

It comes as China rounds off several days of military training around self-ruled Taiwan, a response to Taiwan President Tsai Ing-wen’s recent meeting with U.S. House Speaker Kevin McCarthy in California which infuriated Beijing.

One senior official with direct knowledge of the matter said the flight ban would affect 60%-70% of flights going between Northeast Asia and Southeast Asia, as well as flights between Taiwan and South Korea, Japan and North America.

According to OPSGROUP, an aviation industry cooperative which advises on flight risks, previous restrictions imposed during Chinese military drills last August resulted in significant disruptions to flights in the region, with some pilots forced to carry extra fuel.