Though Chinese airlines allow most personal electronic devices above a certain altitude during flights, restrictions on mobile phones remain in effect.
According to Chinese civil aviation safety regulations, the use of mobile phones is not allowed throughout an entire flight, including takeoff and landing. Violations are subject to fines and other punishment.
Many travelers believe a mobile phone's airplane mode makes them safe to use during flights, but civil aviation authorities have not determined whether the mode can effectively cut off signals from the device, said Zhang Chen, an aviation safety controller with China Eastern Airlines.
"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," he added.
Signals from electronic devices significantly interfere with the airplane's equipment and disturb communication channels with ground control, said Ma Yudong from the Civil Aviation Administration of China's Hubei safety management bureau.
He said manufacturers of mobile phones developed their phones' airplane mode in the absence of a national guideline. Zhang Yun, manager of Air China's in-flight Internet project, said mobile phones will not be adopted in the carrier's in-flight Internet system because they normally have too many signals that will substantially affect a plane's electronic systems.
A report published in 2011 by the International Air Transport Association, a trade group representing more than 230 passenger and cargo airlines worldwide, documented 75 separate incidents from 2003 to 2009 of possible electronic interference that airline pilots and other crew members believed were linked to mobile phones and other electronic devices. The report was based on survey responses from 125 airlines.
Twenty-six of the incidents in the report affected flight controls, including the autopilot, auto-thrust and landing gears. Seventeen affected navigation systems, while 15 affected communication systems.