A commercial pilot has cleared the air on why passengers are still asked to switch their phones to aeroplane mode during flights. Though phones won’t cause planes to crash, signals from connected devices can interfere with cockpit headsets—especially during landings. The issue isn’t life-threatening but can be distracting and frustrating for pilots. The FAA still mandates aeroplane mode, not just for safety, but also as a courtesy. Here’s what really happens when passengers ignore this rule.