He estimated that a typical business passenger could have eight devices powered by 10 lithium batteries on board a flight. Passengers bring an “all-digital rechargeable ecosystem” on board, he said, noting that ULSE’s research has shown that the average passenger boards with four rechargeable devices. This means on a typical narrowbody flight, there could be 700 to 800 devices on board, while a widebody flight could carry 1,500.

Through TRIP, ULSE has been gathering and analyzing thermal runaway incidents since 2019 in partnership with airlines and other safety stakeholders such as ALPA, he said.

Power banks, or portable chargers, have emerged as a critical threat, Wroth said. “A portable charger was responsible for a fire that destroyed an Air Busan aircraft in 2025,” he cited as an example. In that case, everyone was evacuated because the aircraft was still on the ground, and it resulted only in minor injuries.

Recent analysis showed that power banks were the top cause of thermal runaway events in 2025 because nearly every passenger carries one and uses it in flight. Airlines are now highlighting them in preflight communications and updating policies on storage and use.

“Your flight is not just carrying passengers. It’s carrying hundreds, maybe even a thousand small energy storage devices,” he told attendees at the forum. “All [are] classified as dangerous. And these devices are capable of producing heat, smoke, fire, and operational disruption.”

Lithium batteries are safe, he continued, until they are not. “A damaged, defective, counterfeit, crushed, overheated, or even improperly charged battery can enter a state called thermal runaway,” Wroth warned.

He explained that thermal runaway is not a regular fire but rather a self-sustaining chemical reaction causing heat to produce more heat, causing temperatures to rise rapidly, with toxic, flammable gases generated and released. This can cause a fire or even an explosion. “All of this happens in seconds.”

Having said this, Wroth noted that such incidents are rare given the volume of air traffic. But the number and rate of incidents continue to grow as more passengers bring more devices on board. As a result, the number of passenger aircraft thermal runaway events exceeded two per week in 2025 and continues to increase.

“The issue is not whether batteries are dangerous; the issue is that the travel experience for both passengers and crew depends on these devices,” he added. “And that dependency is growing.”

Many passengers have never seen a thermal runaway, and they may not even know they are bringing lithium batteries on board. Fewer than 50% of passengers know the risks, Wroth said. But this is where the issues come in with handling such events.

“They’re going to panic. Some are going to freeze; most of them are going to try to jump up and get away from the fire. And then, you’ve got some Good Samaritans that are going to try to throw water on the fire or maybe put it out in some other way. Most are going to pull out their cell phone and start to record the incident,” he said. “They can easily make the situation worse. They can impede the response of your flight attendants.” If this happens on the ground, the situation could be worse as passengers may begin an uncommanded evacuation.

Passengers should know the cabin crew will respond. “This is where professionalism and airline training shine,” he said. Cabin crew—the “first responders”—will identify the source of smoke, notify the flight deck of the incident, use a fire extinguisher to tamp down visible flames, and then cool the device. The crew will monitor it to guard against reignition and perhaps isolate the device in a thermal containment product—all the while communicating with the flight deck, he said.

Managing the passengers is particularly important since 90% of the incidents occur in the cabin area during flight, Wroth said. Most are controlled before they escalate into a fire.

Beyond safety concerns, these incidents also create operational issues. ULSE estimates that nearly one in five onboard thermal runaway incidents result in a return to the gate, diversion, or unplanned deplaning. Wroth told the pilots in the room, “When a battery incident happens, you may be called upon to make the tough decision.” The flight deck will need to decide whether the flight can continue or whether to turn around or divert. 

“These decisions aren’t made in a boardroom or a conference room. They’re made at 30,000 feet, sometimes over an ocean with incomplete information and your cabin crew trying to control the chaos behind you [while] trying to communicate with you in real time what’s going on,” he said. This is why understanding the problem in advance is important.

“You don’t fight the fire, but you create the conditions that will determine whether the device, the incident, escalates into something catastrophic,” Wroth continued. He advised that pilots treat cabin reports as “high-value intelligence” and understand that reports of odor, smoke, fire, and unusual passenger behavior matter.

Calling crew resource management one of the most effective defenses, Wroth further advised that pilots ask for specifics such as the device involved, location, whether there is smoke and how thick it is, whether there are flames, and what the cabin crew’s response procedures are.

“Good information leads to better decisions. Remember that time is the critical variable,” he said.

Wroth also pointed to FAA guidance emphasizing that extinguishing visible flames is only part of the response, and that cooling and containment are critical because thermal runaway can continue even if the fire is extinguished.