Almost every flight includes the same announcement: switch your phone to airplane mode. Many passengers comply without thinking, and some quietly wonder whether it matters at all. The truth sits between the myths: forgetting airplane mode will not cause a crash, but the rule exists for practical reasons that still apply on a modern aircraft.

The airplane mode rule dates from an era when phones transmitted at higher power and aircraft electronics were less shielded. Regulators took a cautious approach: since a cabin full of transmitting phones had not been exhaustively tested against every aircraft system, the simplest safe policy was to require radios off during critical phases of flight. As phones and aircraft both improved, many regulators relaxed the rule, allowing Wi-Fi and, on equipped aircraft, cellular service through onboard systems. The announcement you hear today reflects your airline's policy and the rules of the country you are flying in, which is why it varies between flights.

Modern aircraft systems are heavily shielded and tested, and there is no documented case of a passenger phone causing an accident. However, phones searching for a signal at altitude transmit at full power and can create audible interference in pilots' headsets, the familiar buzzing you sometimes hear through speakers near a phone. That interference is a distraction during busy phases of flight, which is reason enough for crews to want radios off at takeoff and landing. Onboard cellular systems, where fitted, solve this by giving phones a nearby, low-power signal to connect to instead.

There is also a practical cost to the passenger. At cruising altitude your phone cannot hold a stable connection to ground towers, so it keeps searching at maximum power and drains its battery quickly, while heating up in the process. From the network side, a phone at altitude can be visible to many ground cells at once, which is inefficient for the network. Airplane mode stops both problems at a stroke. It also prevents unexpected roaming charges if your phone briefly connects to a foreign network during a diversion or while taxiing after landing abroad.

The sensible approach is simple: use airplane mode when the crew asks, and re-enable Wi-Fi or Bluetooth if the airline allows it. Download films, music, and maps before departure so you are not dependent on a connection, and remember that the rule is about reducing distraction and interference across hundreds of devices at once, not about any single phone. It costs you nothing to comply, and it keeps the cabin quieter for the crew during the phases of flight when their workload is highest.

Airplane mode does not mean no connectivity at all. Most phones let you re-enable Wi-Fi and Bluetooth while airplane mode stays on, which is how in-flight Wi-Fi works: your phone connects to the aircraft's onboard network rather than to ground towers. That distinction matters, because the onboard system is designed and tested for the aircraft, while a phone hunting for ground towers at altitude is not. Airlines that offer Wi-Fi will usually explain this in their safety briefing, and following their guidance keeps you connected without the downsides.

Bluetooth headphones are generally permitted for the same reason: Bluetooth is a short-range, low-power radio that does not hunt for distant towers. The pattern is consistent across airlines: short-range, controlled connections are fine, while cellular radios searching at full power are not. When in doubt, follow the crew's announcement for your specific flight, since policies differ by airline, aircraft, and country.