Fire in the Sky: Airborne Thermal Runaway Incidents Rise 28% Over 5 Years

Lithium-ion battery fires are frightening in any location; they can seem to happen spontaneously, and they can be notoriously difficult to extinguish. That’s true in homes, where laptop or e-bike batteries may be kept, or on the road, where electric cars and trucks have had incidents. But at least in those places, your local fire department can presumably get to you and hopefully extinguish the blase.

But battery fires become even more alarming in an enclosed airplane at 40,000 feet—far beyond the reach of the firetruck’s hose. It’s no wonder, then, that battery safety in the air is a topic that is being taken seriously by travelers as well as the battery industry.

ULSE reports 28% rise

It’s in that tense context that UL Standards & Engagement (ULSE) releases its lates findings: Battery-related thermal runaway incidents aboard aircraft have reached their highest levels in five years, according to new data ULSE and the Thermal Runaway Incident Program (TRIP) database. From 2019 to 2023, there was a 28% rise in incidents aboard passenger flights, with an average of two cases reported each week.

While incidents have increased, statistically speaking the likelihood of experiencing one remains low, given the roughly 180,000 weekly flights in US airspace.

Related:What Is Thermal Runaway? Here’s a Battery of Answers

Passengers typically bring an average of four rechargeable devices aboard, with smartphones being the most common (82%), followed by laptops (41%), wireless headphones (39%), and tablets (36%). E-cigarettes were the primary cause of thermal runaway incidents in 2023, responsible for 35% of all cases on aircraft, with power banks accounting for an additional 16%.

“Rechargeable devices, especially those stored in passengers’ personal spaces on flights, present risks that must be managed,” stated Lesley Rohrbaugh, head of insights and policy analysis at ULSE. “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.”

In-flight incidents and warning signs

The vast majority of thermal runaway incidents happen on board the aircraft, with 87% occurring during the flight and primarily around passengers’ seats. Almost 60% of these incidents took place in or near the seating area, emphasizing the proximity of devices to potential hazards. Fortunately, most issues are caught early—85% of incidents in 2023 were resolved before reaching the fire or explosion stage. However, 15% escalated to more serious outcomes, illustrating the rapid development of thermal runaway if not addressed swiftly.

Related:PP Compound First to Receive UL Certification for Thermal Runaway Protection of EV Batteries

Checked luggage risks

An increasing number of passengers are packing rechargeable devices, such as e-cigarettes and power banks, in checked luggage, where they pose a greater risk. According to passenger surveys, 27% admitted to placing power banks in their checked baggage, while another 27% checked e-cigarettes. Devices in checked luggage cannot be accessed by crew during a flight, and fires may not be detected as quickly in the cargo hold as they would in the cabin, making this a critical issue for aviation safety.

Addressing the risk: Education and standards

ULSE is working closely with aviation stakeholders to mitigate the risks of battery-related incidents on aircraft. The organization has convened summits and partnerships with airlines, cabin crews, and regulatory bodies, developing safety standards and offering guidance to the U.S. Department of Transportation's Lithium Battery Air Safety Advisory Committee.

“Partnerships across industry, government, and stakeholders are critical to driving progress,” Rohrbaugh emphasized. “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.