Why Power Banks Catch Fire on Flights: The Science of Lithium Battery Risk

An IndiGo flight from Delhi to Chennai was diverted to Hyderabad on 11 October 2026 after smoke was detected from a passenger’s personal electronic device. Cabin crew brought the situation under control and the aircraft landed safely. Reports indicated that the device involved was a power bank stored in an overhead bin. The incident has once again drawn attention to the fire risks posed by lithium-ion batteries during air travel.

The Recent Incident

Flight 6E 6115, operated by an Airbus A321, departed Delhi and was en route to Chennai when smoke was noticed. The airline stated that the cabin crew responded promptly according to established protocols. The pilots then diverted the aircraft to Rajiv Gandhi International Airport in Hyderabad, where it landed safely. A replacement aircraft was arranged to continue the journey for the passengers. No injuries were reported.

Passenger videos circulating online appeared to show an orange glow and smoke coming from an overhead compartment, with some travellers attempting to contain the situation using bags or clothing. The airline’s official statement referred to smoke from a personal electronic device without specifically naming a power bank, though multiple accounts attributed the event to one.

How Lithium-Ion Batteries Work and Why They Can Fail

Most modern power banks rely on lithium-ion or lithium-polymer battery cells. These cells store a large amount of energy in a compact form through controlled electrochemical reactions. Under normal conditions the process is stable and safe. Problems arise when something disrupts that stability.

A manufacturing defect, physical damage, overcharging, or an internal short circuit can initiate a dangerous chain reaction known as thermal runaway. In this process, a battery cell generates heat faster than it can release it. Rising temperatures accelerate internal chemical reactions, releasing flammable gases, smoke and intense heat. Temperatures can climb rapidly, sometimes exceeding several hundred degrees Celsius. Neighbouring cells in a multi-cell power bank can then be triggered in sequence, allowing the fire to spread within the device.

Common triggers include microscopic metal particles left during manufacturing, damaged separators between electrodes, poor-quality materials, or physical trauma such as dropping or crushing the unit. Even if the exterior looks intact, internal damage may exist.

Does Cabin Altitude Make Batteries More Dangerous?

Commercial aircraft cabins are pressurised, but the pressure remains lower than at sea level. Research has examined how reduced ambient pressure affects thermal runaway behaviour. Studies indicate that lower pressure can influence heat transfer and the behaviour of gases released by a failing battery. In some laboratory conditions, the intensity of the fire itself may decrease, while the release of certain toxic or flammable gases can increase.

However, experts emphasise that ordinary cabin altitude is not the primary cause of most battery fires. The main risks remain internal defects, prior damage, overheating and electrical faults. The lower pressure environment may alter the consequences of a failure, but it does not independently make healthy batteries more likely to ignite.

What does change at altitude is the difficulty of managing an incident. At cruising levels, options for immediate response are more limited than on the ground. Smoke and fire in a confined cabin present greater challenges for both passengers and crew.

Why Overhead Bins Increase the Risk

Aviation regulations generally require power banks and spare lithium batteries to be carried in cabin baggage rather than checked luggage. The reason is practical: a fire in the cargo hold may go undetected for longer and is harder to access. Keeping devices in the cabin allows crew to respond quickly if smoke or heat appears.

When a power bank is placed in an overhead bin, detection and intervention can still be delayed. Crew and passengers may not notice the early signs of overheating until smoke becomes visible. Once a thermal runaway begins, conventional fire extinguishers can suppress visible flames but often cannot stop the underlying chemical reaction. The battery may continue to generate heat and can reignite.

Safety Measures and Passenger Responsibilities

Aviation authorities and airlines advise passengers to keep power banks within reach rather than placing them in overhead compartments. Devices should not be charged during flight using aircraft power sources in many cases, and damaged or swollen batteries should never be brought on board. Capacity limits also apply; most airlines restrict power banks above a certain watt-hour rating.

If a device becomes hot, emits unusual smells or begins to smoke, passengers are instructed to alert the cabin crew immediately and avoid attempting to move a failing battery themselves. Crew are trained in specific procedures that may include using water or specialised containment methods once the device is safely accessible.

Broader Context of Battery Incidents

Lithium-ion battery incidents on aircraft have become more frequent as the number of portable devices carried by passengers has grown. Power banks, phones, laptops and e-cigarettes all contain these cells. While the vast majority of flights pass without incident, the consequences of a thermal runaway in a pressurised cabin remain serious enough to justify strict rules and rapid response protocols.

The science behind these events is clear. Lithium-ion batteries pack high energy into small packages. When that energy is released in an uncontrolled manner, the result can be rapid heat generation, flammable gases and fire. Understanding the mechanism of thermal runaway, recognising the contribution of manufacturing quality and physical condition, and following established carriage rules remain the most effective ways to keep the risk low.

The IndiGo diversion serves as a practical reminder that even familiar everyday devices can present challenges at altitude. Careful handling, proper storage and prompt reporting of any abnormality help ensure that the convenience of portable power does not compromise flight safety.

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