The rate of “battery thermal Runaway incidents”—instances of lithium-ion batteries overheating on passenger planes—hit a five-year peak last year, with e-cigarettes being the biggest culprit, according to a report from UL Standards & Engagement (ULSE), a nonprofit organization focused on safety standards.
The data comes from ULSE’s Thermal Runaway Incident Program (TRIP), a voluntary lithium-ion battery incident reporting system. TRIP comprises 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, in a statement. “Thermal runaway incidents on board 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 include:
- Incidents are at the highest point in five years of data collection, rising 28 percent 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.
- The average passenger brings four rechargeable devices on board. Most common items include smartphones (82 percent), laptops (41 percent), wireless headphones (39 percent), and tablets (36 percent). E-cigarettes were responsible for the most incidents in 2023, with 35 percent of reported incidents attributed to vaping devices on passenger flights, followed by power banks, representing another 16 percent of incidents.
- Most incidents happen on the aircraft with devices that are stored near the passenger’s seat. Almost nine out of 10 (87 percent) incidents are reported on the aircraft, with the remaining 13 percent 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 percent of the time.
- The vast majority of incidents are addressed before reaching the fire or explosion stage of thermal runaway. Most (85 percent) incidents in 2023 were addressed when batteries showed warning signs such as overheating and smoking prior to entering full thermal runaway. While only 15 percent 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.
- 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 percent) of travelers reported checking portable chargers, and another 27 percent 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.