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Lithium battery thermal runaway expands aviation insurance risk
WTW links the exposure to how standard extinguishers cannot stop thermal runaway, and notes the FAA logged 93 incidents in 2025, up 4.5% year over year.
Lithium ion battery fires aboard commercial aircraft have become a broader operational exposure for aviation insurers, with a single incident potentially triggering multiple cost categories, including hull loss, passenger injuries, diversions, airport emergency response, cargo claims, and business interruption, WTW said in a new analysis.
WTW attributed the growing risk to thermal runaway chemistry. Once a cell enters thermal runaway, a self sustaining internal reaction can produce rapid heating, fire, toxic smoke, and repeated re ignition, and standard aircraft fire extinguishers may knock down visible flames but cannot stop the underlying chemical reaction. Crews must sustain cooling with large quantities of water or another non alcoholic liquid to prevent spread to adjacent cells.
Regulatory guidance now reflects the suppression versus sustained cooling distinction, WTW said, citing a FAA Safety Alert for Operators that directs aircraft operators to review procedures for overhead bins where a developing incident may go undetected. The FAA recorded 93 lithium battery incidents involving smoke, fire, or extreme heat on US aircraft in 2025, a 4.5% increase from the prior year.
WTW also pointed to incident patterns from prior reporting, including portable chargers accounting for 39% of lithium battery incidents on aircraft reported since 2006, and vape pens accounting for 21%. It added that the FAA data show 18% of in flight incidents led to outcomes such as a diverted landing, return to gate, emergency evacuation, or unplanned deplaning, while aviation battery incidents rose 15% over the five years to 2024, and thermal runaway incidents averaged two per week in UL Standards and Engagements 2024 review.