Chinese forces deployed to the hotly contested South China Sea ordered a US Navy reconnaissance aircraft to “leave immediately” six times Friday, but the pilot stayed the course, refusing to back down.

A US Navy P-8A Poseidon reconnaissance plane flew past China’s garrisons in the Spratly Islands, giving CNN reporters aboard the aircraft a view of Chinese militarization in the region.

Flying over Chinese strongholds on Mischief Reef, Johnson Reef, Fiery Cross Reef, and Subi Reef, CNN spotted “large radar installations, power plants, and runways sturdy enough to carry large military aircraft.” At one outpost, onboard sensors detected 86 vessels, including Chinese Coast Guard ships, which China has been known to use to strong-arm countries with competing claims in the South China Sea.

Lt. Lauren Callen, who led the US Navy crew, said it was “surprising to see airports in the middle of the ocean.”