Airplane mode prevents phones from creating electromagnetic noise that interferes with pilots' headsets.

The primary reason for airplane mode is to prevent electromagnetic interference (EMI) with a plane's sensitive communication and navigation systems. When a mobile device is not in airplane mode, it continuously attempts to connect with cellular towers on the ground. As the aircraft gains altitude and moves away from these towers, the phone increases its signal strength to maintain a connection, which generates significant radio frequency energy.This energy can bleed into the aircraft's audio systems, creating a distinct 'rat-tat-tat' buzzing sound in the pilots' headsets. This phenomenon is similar to the noise once heard when a cell phone was placed near a speaker. For pilots, this noise is more than just a nuisance. It can mask critical verbal instructions from Air Traffic Control during high-stakes maneuvers like takeoff and landing.The Federal Communications Commission (FCC) first established rules against in-flight cellular use in 1991 to protect ground networks from interference. While modern avionics are heavily shielded, the sheer volume of personal electronic devices on a typical flight poses a cumulative risk. Organizations like the International Air Transport Association (IATA) continue to support these restrictions to ensure the integrity of the 108 to 137 MHz frequency band used for aeronautical voice communications.In 2013, the Federal Aviation Administration (FAA) relaxed rules to allow the use of 'non-transmitting' electronics during all phases of flight. However, the requirement for airplane mode remains strictly enforced for cellular transmissions. This safety protocol ensures that the cockpit remains a quiet environment free from avoidable technical distractions.