Between Jan. 5 and Feb. 6, police in Beijing detained three passengers for allegedly using their mobile phones during flights, the Civil Aviation Administration of China (CAAC) announced this week. And while the use of phones on flights is often curtailed all over the world, both the wide scope of the arrests and the severity of the punishment may surprise some readers.

In one case, for example, a passenger was detained for five days. This person's alleged crime? Listening to music on their phone during takeoff and landing.

China has long been one of the only nations in the world to order that phones be completely turned off during flights — even turning the phone to airplane mode isn't enough in most cases, according to official CAAC rules. And though these rules are not always enforced rigorously, they can carry harsh penalties: Aside from detention, passengers can be fined up to 50,000 yuan ($7,264) for using their phone, according to Chinese media.

Confusingly, the rules only apply to mobile phones and not other electronic devices such as tablets. During a 2014 interview with the travel website Skift, an aviation safety controller with China Eastern Airlines explained that the problem was that many airplane modes don't always cut off signals from the phone completely.

“You can use any mobile phone to dial an emergency hotline even if it has no SIM card or is in airplane mode, which means it can search or send signals under these conditions,” Zhang Chen said.

For foreign travelers in China who use their phone to amuse themselves during their domestic flights, it can be an especially frustrating experience. And as other countries have further liberalized their own rules about electronic devices, China has been left further and further behind.

There have been hints that rules would be changed soon. In 2014, Zhou Hong, an aviation communication expert, told China Daily that the CAAC had been “exploring the possibility of air travelers using electronic devices at a height of more than 3,000 meters,” or roughly 9,842 feet. Hong suggested that the result of the study would come in 2016.

Last year, as that deadline came and went, there was another report that China would allow mobile phone usage on flights. In an interview with Bloomberg, Zhu Tao, director of the air transportation division at CAAC, told Bloomberg News that he expected legislation to be amended either by the end of the year or by early 2017.

Given that both domestic air travel and mobile phone use have skyrocketed in China over the past few years, any changes to the rules are likely to be popular.

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