Li-ion Thermal Runaways on the Rise in Aircraft Cabins

Lithium-ion battery thermal runaway incidents on passenger flights rose 15% from 2024 to 2025, according to the UL Standards & Engagement (ULSE) Lithium-ion Battery Incidents in Aviation: 2025 Data Review. Portable charger incidents rose 42%, making them the leading culprit ahead of e-cigarettes, with cell phones the third most common device involved in thermal runaways.

ULSE gathers information from its leading voluntary Thermal Runaway Incident Program (TRIP), which includes more than 40 passenger and cargo airlines submitting information to the TRIP database. According to ULSE, the rate of weekly incidents has reached 2.36, up from 2.05 in 2024. The cost to the industry now averages $1.8 million a year, or $96,000 per incident, “in damage, disruption, and associated losses.”

Passengers are still packing lithium-ion battery chargers in the worst possible place: in bags stored in the baggage space, which cannot be accessed in flight on airliners but can be in some business jets. “There are limited options to fight fires in the cargo hold: typically only through means such as halon extinguishers and oxygen-depriving systems,” ULSE explained. “However, these methods are not effective on lithium-ion battery fires, which are more difficult to extinguish and more likely to reignite compared to other materials.”

To mitigate the risk of thermal runaway incidents, ULSE recommends cabin crew training, standards for onboard safety equipment to help manage thermal runaways, and more passenger education. ULSE has developed a safety standard for fire-containment bags or boxes—UL 5800—and noted that while the FAA doesn’t require this equipment, “some airlines have taken the initiative to stock their fleets. Efficacy and ease of use are essential to mitigating battery fires using these products.”

“Every incident is a safety risk, and the trend line is moving in the wrong direction,” said ULSE president and CEO Jeff Marootian. “Passengers do not need to be safety experts to reduce the risk. Keeping rechargeable devices within reach can help us all fly in safer skies.

“Airlines are taking the risk seriously, strengthening policies and training crew to respond when incidents occur. But they cannot solve this problem alone. Passengers need to understand the risks and know what to do before the rechargeable device becomes a safety threat,” he added.