Chinese jets repeatedly buzzed a Canadian plane monitoring North Korea, sometimes coming so close that the pilots could see each other. Hundreds of miles to the south, a Chinese fighter plane sprayed metallic chaff in the path of an Australian surveillance craft, a maneuver that Australia called "very dangerous.”

To Chinese officials, these were reasonable responses to foreign military patrols that threatened China’s security. To the U.S. allies, the Chinese pilots’ actions in recent weeks were worrying escalations, risking a midair collision or crash.

Such a mishap could trigger a broader conflict. "There are split-second differences between this being a passing headline and this being a major incident with enduring international ramifications,” said John Blaxland, a professor of security and intelligence studies at the Australian National University in Canberra.