New Data: Battery Thermal Runaway Incidents on Board Passenger and Cargo Aircraft Hit Record High as Passengers Remain Largely Unaware of Risks

Washington, D.C. - Today, UL Standards & Engagement released a report showing a 28% increase in battery thermal runaway incidents – a record high – on aircraft and limited passenger awareness of the dangers of lithium-ion batteries during air travel. For the first time, ULSE is publicly sharing data from its Thermal Runaway Incident Program, a voluntary lithium-ion battery incident reporting system, to clarify the problem and support identifying solutions. 

TRIP is comprised of 35 passenger and cargo airline participants. The program was designed with the aviation industry to better understand the extent of thermal runaway incidents caused by lithium-ion batteries onboard aircraft and how to prepare for, or ideally prevent, future incidents.

“Passengers are often unaware that many devices they bring on board are powered by lithium-ion batteries, let alone the risks they carry, and it’s much harder to solve a problem that they do not know exists,” said David Wroth, director of technology and systems at ULSE and the leader of TRIP. “Thermal runaway incidents onboard aircraft are largely preventable but admittedly more difficult to contend with at 40,000 feet. TRIP provides a unique opportunity for the aviation industry to come together to find strategies to mitigate the risk of these incidents.” 

As technology evolves and more products rely on rechargeable power, lithium-ion batteries are getting more powerful and in some cases larger, further complicating the thermal runaway threat. Damaged, substandard, or counterfeit batteries run the greatest risk of going into thermal runway, presenting serious consequences in flight.  

Key takeaways from the report: 
 

1. Incidents are at the highest point in five years of data collection. Incidents rose 28% over the past five years, from 2019-2023. There are an average of two thermal runaway incidents reported in the TRIP database each week. While on the rise, with approximately 180,000 flights in U.S. airspace per week, it is still highly unlikely to experience a thermal runaway incident.
2. The average passenger brings four rechargeable devices on board. Most common items include smartphones (82%), laptops (41%), wireless headphones (39%), and tablets (36%). E-cigarettes were responsible for the most incidents in 2023, with 35% of reported incidents attributed to vaping devices on passenger flights, followed by power banks, representing another 16% of incidents.
3. Most incidents happen on the aircraft with devices that are stored near the passenger’s seat. Almost nine out of ten (87%) incidents are reported on the aircraft, with the remaining 13% occurring when baggage and personal items are on the move. On the aircraft, thermal runaway incidents occur in or around the passenger’s seat nearly 60% of the time.
4. The vast majority of incidents are addressed before reaching the fire or explosion stage of thermal runaway. Most (85%) incidents in 2023 were addressed when batteries showed warning signs such as overheating and smoking prior to entering full thermal runaway. While only 15% of incidents resulted in fire or explosion, the speed in which thermal runaway can develop means that the events in the majority could have been more serious had the issue not been addressed quickly.
5. Rechargeable devices are being packed in checked luggage. The devices that were most cited in thermal runaway incidents in 2023 were also the two most frequently put in checked luggage, according to passengers surveyed. More than a quarter (27%) of travelers reported checking portable chargers, and another 27% said they checked e-cigarettes. Devices that enter thermal runaway in checked baggage cannot be accessed by crew while in flight, and fires may not be detected as quickly in the cargo hold as they would be in the cabin.

“Our research highlights several trouble spots that need to be addressed, from passengers missing warnings about lithium-ion batteries to packing rechargeable devices out of reach,” said Lesley Rohrbaugh, head of insights and policy analysis for ULSE. “But we also see clear opportunities to reduce the risk and that’s where we’re focused.” 

Through additional passenger and cabin crew focus groups and interviews conducted by ULSE and data from TRIP, strategies to reduce these risks include passenger education, cabin crew training, and standards for aircraft baggage handling. 

ULSE convenes summits with aviation stakeholders twice a year, works with industry groups through partnerships and presenting at events and meetings, and has developed safety standards for aviation.  The organization is also represented on the Department of Transportation's Lithium Battery Air Safety Advisory Committee 

“Partnerships across industry, government, and stakeholders are critical to driving progress,” continued Rohrbaugh, who also serves as a subject matter expert to LiBASAC along with David Wroth who is a member of the committee. “Our role is to serve as a resource to stakeholders by providing information that can help drive change and make air travel even safer.”

Read the full report here. 

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Methodology:  

All studies were designed and formulated by UL Standards & Engagement. 

Quantitative results were primarily taken from a ULSE Insights survey series of a cumulative 8,076 U.S. adults, conducted between August 2023 and December 2023. Surveys were administered online by BV Insights. As a member of the Insights Association and ESOMAR (the European Society for Opinion and Marketing Research), BV Insights adheres to industry ethics and best practices, including maintaining the anonymity of respondents. 

The margin of sampling error at 95% confidence for aggregate results is +/- 2.2%. Sampling error is larger for subgroups of the data. As with any survey, sampling error is only one source of possible error. While non-sampling error cannot be accurately calculated, precautionary steps were taken in all phases of the survey design and the collection and processing of the data to minimize its influence. 

Passenger qualitative data was derived from two focus groups administered by YouGov in July 2024. Focus groups were conducted with a total of 24 passengers, 12 of whom had been on >7 flights in the past 12 months, and 12 of whom had been on <7 flights in the past 12 months. Passengers were a combination of business and leisure travelers and represented a mix of demographic groups as well as travel with and without children.

Additionally, ULSE held seven in-depth cabin crew interviews (n=7) and six focus groups (n=41) focused on cabin crew experiences for a total of 48 participants. All qualitative data was transcribed, uploaded into the MAXQDA software platform, and analyzed with a hybrid coding frame.

Note: All numbers are percentages unless otherwise noted. Figures may not total 100% due to rounding. 

About ULSE

UL Standards & Engagement is a nonprofit organization that translates safety science into action through standards development, partnerships and advocacy. Since 1903, we have developed nearly 1,700 standards and guidance documents for products ranging from fire doors to autonomous vehicles. ULSE enables innovation and grows trust by convening experts and informing policymakers and regulators as we work toward a safer, more secure and sustainable future. Visit ulse.org for more information.

Contact

Catie Talenti
UL Standards & Engagement
Senior Strategic Communications Specialist
P: (607) 742-8766
catie.talenti@ul.org