A Lufthansa aircraft was forced to divert and land in the French city of Lyon the previous Saturday after a portable power bank caught fire on a flight from Frankfurt to Lisbon carrying 198 passengers.
How battery damage turns into a fire
The company said the crew placed the battery in a protective bag designed for lithium batteries, confirming that no injuries were reported. The incident has refocused attention on the risks posed by lithium batteries carried by passengers on aircraft, particularly as reliance on external batteries to charge phones and electronic devices grows.
Although these batteries are considered safe under normal conditions, damage, excessive heat or overcharging, along with a possible manufacturing defect, can cause them to enter a state known as thermal runaway.
The US Federal Aviation Administration explains that thermal runaway can begin without warning, with the battery’s temperature rising rapidly and the reaction inside it producing smoke, flammable gases or fire. The danger does not necessarily end when the flames disappear, because extinguishing the fire does not always stop the thermal reaction inside the battery, making cooling essential to prevent it from continuing or restarting.
Lithium incidents rise, with power banks the biggest source
Data presented by David Roth, vice-president of standards, technology and operations at UL Standards and Engagement, show that lithium battery incidents on aircraft rose by 15% in a year, with power banks becoming the biggest source of such incidents.
Roth made the remarks at the Air Line Pilots Association’s aviation safety forum, held in Washington in mid-September 2026. According to Roth, the rate of thermal runaway incidents on passenger aircraft exceeded two a week during 2025.
The organisation’s data also show that each passenger carries an average of four rechargeable devices. This means there are about 700 to 800 devices on a small aircraft, while the number can rise to 1,500 on larger aircraft.
How batteries affect flight routes
These incidents have a direct impact on flight operations: one in five results in the aircraft returning to its departure gate, diverting to another airport or passengers being disembarked unexpectedly. In January 2025, a South Korean Air Busan aircraft caught fire and was completely destroyed while on the ground. Investigators believed the fire started with a portable power bank inside an overhead baggage compartment.
For this reason, safety rules require passengers to keep power banks in the aircraft cabin rather than placing them in checked baggage in the hold. If a battery begins to heat up or emit smoke in the cabin, passengers and crew can spot the problem and reach the device quickly, unlike a battery inside a bag in a hold that cabin crew cannot access during the flight.
Under this rule, external batteries must be carried in hand luggage. If an airline decides to move a passenger’s cabin bag to the hold at the boarding gate, the power bank must first be removed and kept in the cabin in line with approved safety requirements.
New ICAO rules on the number and use of batteries
Lufthansa had introduced similar restrictions before those rules were adopted, banning the use or recharging of external batteries on its aircraft since January, while continuing to allow passengers to carry a maximum of two batteries, provided they complied with safety requirements.
Regarding battery capacity, IATA guidance sets 100 watt-hours as the limit for portable charging batteries that may be carried under the usual rules in the cabin. If the watt-hour rating is not marked on the device, it can be calculated by multiplying the voltage in volts by the capacity in ampere-hours.
For example, a battery with a capacity of 20,000 milliampere-hours and a voltage of 3.7 volts is equivalent to about 74 watt-hours. If a battery becomes hot, swells or emits smoke during the flight, passengers should notify the crew immediately and not attempt to handle it themselves, allowing the crew to isolate and cool it in accordance with procedures for dealing with lithium batteries.
