EasyJet flight EZY2618 was somewhere over the Adriatic Sea when the woman approached a crew member and made the confession.
Her checked baggage contained something it shouldn't have: a lithium-ion battery connected to a device.
The plane was midway from Hurghada, Egypt, to Luton, when the captain decided to make an emergency landing at Rome's Fiumicino Airport. Memories of Air Busan Flight 391, which was engulfed in flames and destroyed by a suspected faulty battery pack in January 2025, likely flashed through his mind.
The plane landed safely in Rome, and the passengers flew back to Luton the following day. But the reason for the diversion—the lithium-ion battery—remains one of the biggest threats to modern aviation. Now, safety experts are urging airlines to take this danger more seriously.
Hidden Risk of Battery Pack
According to estimates from the UK Civil Aviation Authority (CAA), 96 percent of air passengers carry devices that use lithium-ion batteries. These include phones, laptops, iPads, portable chargers, and e-cigarettes. On average, each passenger carries four such devices per flight.
Between 12 and 14 million people travel by air every day worldwide, meaning that approximately 50 million lithium-ion battery-powered devices are carried on board planes every day, or 350 million per week.
Of these 350 million devices, on average, only two per week suffer from so-called thermal runaway—a self-sustaining, uncontrolled series of electrical failures and chemical reactions. Anyone who has witnessed this on an airplane knows it's more than just sparks and smoke.
In 2025, Air Busan Flight 391 was engulfed in flames due to a faulty lithium-ion battery pack — Shutterstock
«"If a lithium-ion battery is crushed, overcharged, overheated, or if it contains defects or contamination, chemical processes occur that generate enormous amounts of heat and gas," said Paul Christensen, a professor at Newcastle University and a leading expert on lithium-ion battery safety.
«"I saw a video of flight attendants opening the overhead bins and getting a cloud of steam in their faces. That's bad news," he added.
Within the vapor cloud is what Christensen describes as a "witch's brew" of chemicals: carbon monoxide, ethane, methane, hydrochloric acid, cyanide, and organic droplets that can condense in the lungs. Scientists are only just beginning to understand the dangers these substances pose to human health.
«"We're starting to hear about people who have suffered life-changing injuries from inhaling steam clouds after thermal runaway," he says. One firefighter in Sacramento inhaled a toxic steam cloud emitted by an electric vehicle just once. He was out of work for 10 months.
What about the worst-case scenario? An average-sized battery with a capacity of 10 milliamps can produce 20 liters of gas, which is not only toxic but also explosive.
«"If ignition occurs, there will be flashes of flame that could easily reach temperatures of 1,000 degrees Celsius," says Christensen. "This hasn't happened yet, and hopefully never will, but if this vapor cloud escapes and ignition is delayed, it could lead to an explosion.".
Previous incidents
An Air Busan flight from Gimhae International Airport in South Korea to Hong Kong was scheduled for January 2025.
A fire broke out moments before takeoff. Video footage shows the plane engulfed in flames, with thick smoke billowing from the cabin. Nearly half the fuselage was destroyed, with large holes in the upper portion of the plane revealing seats and smoldering luggage.
All 169 passengers and seven crew members evacuated the aircraft via inflatable slides. Seven people were taken to the hospital. An investigation revealed that the most likely cause of the fire was a compressed battery pack in the overhead compartment above the seats at the rear of the aircraft.
Hundreds of dangerous situations have occurred in recent years, including an incident on a T'way flight from China to South Korea, during which a passenger's portable charger emitted a cloud of toxic fumes. In such cases, flight attendants are trained to dispose of the device in water, sand, or a special bag designed for storing discharged lithium batteries.
«"There is no ideal place for a lithium battery to ignite on board an aircraft, but the cabin is the most likely place for a fire to start," says Jonathan Nicholson of the Civil Aviation Authority.
As a result, most airlines ask passengers not to leave lithium-ion batteries in their suitcases. Knowing that batteries will inevitably be carried in checked baggage, airlines have taken steps to strengthen fire prevention measures. Flight attendants have no way to access the baggage compartment during the flight – there are no hidden steps or hatches – meaning these processes must be automated.
«"There's a fire suppression system in the hold, but it's not effective enough to deal with something in the cabin," says Nicholson. "Typically, they're sprinkler systems. Large containers can also contain a fire to a certain level. But that's not ideal. No crew wants a fire in the hold.".
«"If a pilot has the ability to change course, he will. But if it's a transatlantic, mid-Atlantic, or mid-Pacific flight, the situation will be unpleasant.".
«"We need to educate the public so they don't do stupid things.".
Devices powered by lithium-ion batteries will never be completely banned on board aircraft. In fact, some airlines, such as Ryanair, now require all passengers to present a digital pass to board the plane.
So the solution lies in public education.
«"Passengers need to know one thing: don't put pressure on these devices. Computers, phones, batteries—pressure is harmful," says Dr. Hasan Shahidi, executive director of the Flight Safety Foundation. "That's why they say you shouldn't try to retrieve your phone [if you dropped it during a flight]. They don't want the seat adjustment to put pressure on the phone and battery.".
As devices with lithium-ion batteries become more common, airlines are taking steps to strengthen fire prevention measures — E+
Almost all airlines prohibit portable chargers from being carried in the hold. However, some, such as Qantas, prohibit the use of rechargeable batteries on board. Others, including BA, do not.
«"We see that different airlines have different rules. This can also be confusing for passengers. They fly with one airline, which has one set of rules, and then board another airline with different rules. This is worrying," says Shahidi.
According to a survey conducted by the Civil Aviation Authority of Canada, 29 percent of air passengers believed lithium-ion batteries should be checked in baggage. About 15 percent were unaware of any restrictions.
At the end of June, the Civil Aviation Authority of Canada will launch an information campaign about lithium batteries on board aircraft, which will follow the International Air Transport Association's "Travel Smart with Lithium Batteries" campaign, which ran in 2025.
«"We need to educate the public about not doing stupid things with batteries," says Christensen. "It's the little things that need attention: check your batteries for visible damage, do they get very hot? Did you buy them from a reputable company? Are they swollen?"»
Flight attendant safety training has increased significantly in recent years, but Christensen says airlines haven't taken enough action.
«"They may have been told to dump it in a bag, but they don't know that this vapor cloud isn't smoke. And they certainly don't know that it's explosive. I guarantee that 99.9% airline personnel aren't informed about the risks and hazards at the level of detail that's required.".
Christensen said he recently flew on a flight that included a passenger with a disability who brought a large battery for his scooter.
«"During the flight, I calculated the likely consequences of an explosion and gas release and what measures could be taken to prevent it. I figured that if we had a carbon dioxide fire extinguisher on board, we could detonate it and keep the gas concentration below the lower explosive limit.".
«"I asked the flight attendant what kind of fire extinguisher was on board. He leaned over and said, 'Red, sir.'".
«"I came to the conclusion that such a display of aggression would be extremely bad news.".
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