China frequently organizes military exercises in the skies over south China which result in delays to passenger aircraft, but this case appears to stand out from the rest.

A Vietnamese news website is reporting that Vietnam Airlines plane VN416 from Hanoi to Seoul was ordered to fly over Guangzhou for 55 minutes on January 15, resulting in delays of several hours as the flight had to make an emergency landing in Shanghai to refuel.

Chinese Air Traffic Control reportedly give the instruction to the pilot of VN416 due to “dangerous activity in the area”.  Now Vietnam wants to know what happened:

Lai Xuan Thanh, vice chief of the Civil Aviation Authority of Vietnam, announced the news and added he had suggested the Chinese agency to make explanation about the incident.

In law, a passenger plane which is operating in the airspace of a nation has to comply with instructions of the nation’s aviation authority.

The article notes avoiding a military exercise is not rare, but normally a quick explanation is given, which makes this a bit more perplexing.