Disputed South China Sea airspace that Beijing claims as its own falls within Manila’s Exclusive Economic Zone, where the Philippines and other countries enjoy freedom of overflight.

"The Philippines has no major external security threats, but has turned itself into a country that undermines regional peace and stability through a militarization carnival," said Ding Duo, director of the Research Center for International and Regional Issues at the National Institute for South China Sea Studies.

A Philippine plane warned a Chinese military helicopter over the South China Sea that it was "flying too close," as tension between the U.S. ally and Beijing soars.