It’s no secret that China despises the pesky US drones and spy planes circling above the South China Sea, seen by Beijing as the nation’s aquatic backyard.

But now the People’s Republic of China can do more than tell American pilots to buzz off. It can more easily blow them right out of the sky.

Sometime last week, according to officials from the US and Taiwan, China appears to have placed surface-to-air missiles right in the middle of the planet’s most contested waters. These HQ-9 missiles, developed by China’s own military, have a range of roughly 125 miles.

Practically any aircraft flying near the missile system is now within China’s sights. That includes a steady flow of drones and surveillance jets operated by the US, which contends that the sea should be an international free-flow zone largely defended by American warships.

The HQ-9 missiles aren’t minor-league weapons. “They’re one of the best pieces of equipment in the Chinese inventory,” says Richard Bitzinger, a defense expert with the S. Rajaratnam School of International Studies in Singapore.