Most airlines note that there is a chance that radio signals sent out from an electronic device could interfere with one or more of an aircraft's important systems, such as sensors that help the aircraft's instruments communicate with one another, navigation equipment, collision-avoidance equipment, and other forms of ...

Airlines require you to switch your phone to "Airplane Mode" (or off) primarily to prevent Electromagnetic Interference (EMI) with the aircraft's sensitive navigation and communication systems. While modern planes are shielded against most consumer electronics, the collective signals from hundreds of phones constantly searching for a network can create "cumulative interference." This is particularly critical during the high-stakes phases of takeoff and landing, where pilots rely on precise radio altimeters and GPS data that operate on frequencies close to those used by 5G mobile networks. Beyond technical safety, there is a "human factor" involved: flight crews want your full attention during the safety briefing and in the event of an emergency. A distracted passenger with headphones on is less likely to hear life-saving instructions. Finally, at high altitudes, your phone's attempts to connect to ground-based cell towers at 500 mph can actually overload the cellular network on the ground, as your device rapidly "hops" between towers, causing signal confusion for the provider.