The incident happened just two days after the PLA sent a record 28 planes to the island’s ADIZ.

Observers said the latest fly-by – which involved two newer-model J-16 fighter jets, four old model J-7 fighters and one Y-8 electric warfare aircraft – was aimed at testing interoperability of its two generations of planes, reports The South China Morning Post

It was also intended to test their ability to counter electronic interference, they told the newspaper.

Relationships between Taiwan and China have touched low points in recent years.