Airplane Mode

Just as it is hard to catch a whisper across a noisy room, radio emissions from smartphones can create subtle electromagnetic noise for an airplane's sensitive avionics. Throughout a flight, aircraft continuously exchange radio transmissions with air traffic controllers on the ground while calculating position and altitude using GPS satellites and onboard navigation equipment. Ground radar stations track the plane along its entire route.

When hundreds of passengers on an airliner transmit wireless signals simultaneously, eliminating the chance of radio interference is difficult. While there is no definitive proof that a phone has caused a plane crash, aviation regulations take an intentionally strict precautionary approach. Furthermore, at lower altitudes during takeoff and landing, phones attempt to ping multiple ground cell towers at once, congesting terrestrial cellular networks. You might recall placing an older phone next to an audio speaker and hearing a rhythmic buzz or chatter. In the era of 2G mobile phones, pilots reported similar static in their cockpit headsets, though this is far rarer with modern LTE and 5G networks.

Takeoff and landing are the flight's most critical phases, relying heavily on ground communication and precision landing aids like the Instrument Landing System (ILS). Because any interference with navigation instruments could pose a safety hazard, aviation authorities require passengers to enable this setting to halt all radio transmissions at once.

Smartphones are designed to ramp up their transmission power when cellular reception is weak, much like someone shouting louder across a long distance. This power boost is why your device often gets warm on the back when searching for a faint signal.

Cruising at 30,000 feet, your phone is physically too far from ground cell towers to receive a reliable signal. If you leave airplane mode off, your phone will endlessly search for cell networks and boost its transmitter output to connect to the faintest whisper of a signal.

This continuous search overworks the processor and wireless modem, generating heat and draining your battery quickly. Turning on airplane mode immediately stops the useless search for cell towers, extending your battery life significantly and even allowing the phone to charge a bit faster since no power is wasted on signal hunting.

While airplane mode shuts off all radios by default, you can manually switch Wi-Fi or Bluetooth back on in your device's settings menu. Many modern phones even remember your preference and keep Bluetooth on automatically. There are good technical reasons for handling these connections differently.

Cellular signals (LTE and 5G) must travel miles to reach towers, and at high altitudes, phones try to ping multiple ground stations at once, overwhelming ground networks. In contrast, Bluetooth uses tiny, low-power signals that reach only a few yards, and Wi-Fi communicates strictly with onboard routers located inside the cabin. Aviation regulators, including the US Federal Aviation Administration (FAA) and European authorities, studied consumer electronics and relaxed rules around 2013 to 2014, allowing devices in airplane mode to be used gate-to-gate.

Today, depending on the country and airline, carriers routinely permit short-range wireless connections so passengers can use in-flight Wi-Fi or listen to music through wireless earbuds. Guidelines on when and where you can use them vary by carrier. Regulators do not ban every signal indiscriminately; rather, they separate high-power long-distance cellular transmissions from low-power short-range connections.