North Korea’s state-owned airline, Air Koryo, apparently pushed China’s civil aviation regulators beyond the limits of their patience with an emergency-landing incident last month. On Wednesday, China announced that Air Koryo’s operations would be limited until significant improvements in pilot training and maintenance are made.

The emergency landing was made by a Russian-built Tupolev TU204-300 plane, en route from Beijing to Pyongyang, North Korea, when smoke was detected in the cabin. The plane made an emergency landing in the Chinese city of Shenyang.

Reuters describes a scathing report from China’s aviation authorities:

China’s civil aviation regulator, in a statement on Wednesday, said an investigation had found smoke had come from a call button located under the luggage rack on the right hand side of the cabin between rows 20 and 27.

The regulator said they had found three problems that happened during the emergency that the airline now had to fix.

The airline has to improve training on how to handle such an incident, how to communicate with air traffic control and improve aircraft maintenance, it said.

The airline also needs to improve training on handling burst tyres, engine fires, emergency decompression and traffic collision avoidance system warnings, the regulator added.

Reading between the lines, it sounds like whatever the pilots did during the emergency was vexing to the Chinese air traffic controllers, and to at least this one civil aviation regulator. (Notably, Reuters reports Air Koryo officials said they knew nothing about the operational restrictions, and the Chinese regulator did not specify exactly what those restrictions would entail.)

The Wall Street Journal explains that China’s regulatory system works on “demerit points for safety violations and other missteps,” with punishments “ranging from restrictions on aircraft use to suspension of their operations.” Air Koryo racked up four demerits in this particular instance, which sounds pretty bad.

In theory, four demerits could restrict Air Koryo from “adding new aircraft and destinations in China,” but that does not seem likely in any event. The airline has been operating since the 1950s but only flies to three destinations — Beijing, Shanghai, Shenyang, and Vladivistok in Russia. The WSJ recalls that the European Union banned Air Koryo in 2006 due to safety concerns, relenting in 2010 to permitting flights from the newest jets in the fleet.

Unsurprisingly, the North Korean airline gets very low ratings from consumer agencies — the only 1-star airline in the world, according to Skytrax.

Every now and then, someone sneaks a video recording out of an Air Koryo jetliner, to give the outside world an idea of what the service is like. For example, the in-flight safety videos include regime propaganda, extolling the virtues of the Kim family’s great Communist revolution, and the in-flight “entertainment” consists of more propaganda videos: