Putting a smartphone in checked luggage is generally discouraged by both airlines and safety experts for two primary reasons: theft and fire safety. Lithium-ion batteries, which power all modern phones, are considered "dangerous goods." While a single phone is typically allowed in the hold, if the battery were to experience a "thermal runaway" (overheating and catching fire) in the unmonitored cargo hold, it could be catastrophic. In the cabin, such fires can be quickly extinguished by crew members. Furthermore, checked bags are subject to rough handling and potential pilferage; smartphones are high-value, easily sold items that are frequently targeted by dishonest baggage handlers. In 2026, baggage tracking technology has improved, but it doesn't prevent physical damage from the crushing weight of other suitcases. If you must check a phone, you should power it off completely (do not leave it in sleep mode), wrap it in several layers of soft clothing to absorb shocks, and use a suitcase with a TSA-approved lock. However, the "gold standard" for travel remains keeping all electronics with batteries in your carry-on bag for both the safety of the flight and the security of your device.