China's patience with North Korea has been gradually wearing thin. Six-party talks organised by Beijing in 2003 to bring the North to heel over its nuclear weapons programme have achieved little and been stalled since 2012. Relations have been strained after weapons tests and leader Kim Jong-un's regime ignored warnings. In the circumstances, the near-miss of a Chinese airline by a recklessly fired missile should have elicited a tough response.

The missile was one of seven fired on March 4 by the North as a show of strength during war games between the US and South Korea. It missed the China Southern plane carrying 220 people from Japan to Shenyang by just seven minutes; China was not alerted, nor were the aircraft's crew aware that the jet was flying along the rocket's trajectory. North Korea has no closer ally, but even among nations with firm relations, such an incident would provoke an angry response. Beijing's tone was measured, though; it expressed little more than concern that international practice had not been followed.

China does not want a nuclearised Korean peninsula, but it has to handle delicately its dealings with the North. China is the isolated country's biggest trading partner and main source of food, fuel and investment. Although Beijing has twice backed UN sanctions against Pyongyang after nuclear tests, it is reticent about implementing harsher measures for fear of regime collapse and a flood of refugees across their shared 1,290-kilometre border. The US, South Korea and Japan are apt to forget such possibilities when calling on Beijing to get tough.