A Chinese naval helicopter flew nearly 10 feet from a Philippine patrol plane on Tuesday over a contested reef in the South China Sea, escalating tensions with Manila and Washington in the airspace over international waterways Beijing claims as its own.

A Chinese military helicopter flew within 10 feet (3 meters) of a Philippine patrol plane over the South China Sea on Tuesday, in what observers said was the second incident of potentially catastrophic behavior by the People’s Liberation Army against foreign aircraft in a week.