“A customer’s battery charger apparently overheated and began to smoke.” Just one day after implementing its “first-in-industry” portable charger policy, Southwest Airlines released a statement that highlights a rapidly growing problem for contemporary air travel: the safe transportation and use of lithium-ion batteries at altitude.
After a portable charger in the cabin began to emit smoke, Flight 1844, a regular flight from Baltimore to Tampa, was forced to make an abrupt right turn toward Myrtle Beach, South Carolina. The captain quickly diverted the Boeing 737 for an emergency landing, and flight attendants quickly isolated the device in a fire containment bag. Although all passengers were unharmed, the incident made it clear that lithium battery incidents are becoming more frequent and are not merely hypothetical threats.
It was oddly timed. Twenty-four hours prior, Southwest had implemented a rule that prohibited passengers from charging their phones in overhead bins or carry-on luggage and required them to keep power banks visible while in use. It will no longer be allowed to use portable charging devices inside of bags or overhead bins. Southwest said in an email to CNET that “Using portable charging devices while stored in a bag or overhead bin will no longer be permitted. Nothing is more important to Southwest than the safety of its customers and employees.” Southwest joins an increasing number of international airlines that have tightened regulations on battery-powered devices in response to recent incidents. AirAsia, Thai Airways, and all South Korean airlines have already implemented similar measures.
Science is the foundation of the reasoning. Thermal runaway is a common occurrence with lithium-ion batteries, which power devices like e-cigarettes and smartphones. According to Deke Ezekoye, an engineering professor with the University of Texas Fire Research Group, thermal runaway is a process that takes place inside the cell. “Within the cell, there’s a process called ‘thermal runaway’ that occurs.” Internal short circuits, physical harm, overcharging, or exposure to extremely high or low temperatures can all cause this self-replicating reaction. Once started, the battery produces its own heat and even provides its own oxygen, making it challenging to put out the fire, even when submerged, as shown in lab experiments.
The implications are not hypothetical. The first five months of 2025 saw 22 battery-related incidents on flights, up from a record 89 in 2024, according to the Federal Aviation Administration. According to industry analysis, fires involving lithium-ion batteries on airplanes have increased 388% since 2015 and now occur almost twice a week on average. Although there is very little room for error at 40,000 feet, the great majority of these incidents are contained before developing into full-fledged fires or explosions.
An Air Busan flight in South Korea was evacuated in January after a power bank kept in an overhead bin caught fire, causing seven injuries and destroying a portion of the aircraft’s roof. Deteriorated insulation within the battery was identified by investigators as the cause. As part of a larger regulatory reform, South Korea responded by outlawing the storage of power banks in overhead bins and mandating that all lithium-powered devices be kept within passengers’ reach while in flight.
Thermal runaway mechanics are both dramatic and hazardous. When a lithium-ion cell malfunctions, it can reach temperatures of 1,300 degrees Fahrenheit and release harmful gases like carbon monoxide and hydrogen fluoride. Poison is created by the combination. In a technical briefing, toxicologist Dr. Richard Pleus told NBAA, “The combination makes poison. I’m concerned about being in an aircraft cabin with a fire causing these gases to reach levels that might incapacitate a person.” Most fumes can be removed by modern aircraft ventilation, but the first few seconds are crucial.
As part of their response training, flight attendants frequently use specialized containment bags made to isolate overheating equipment. Although these bags work well to contain flames and stop a fire from spreading, they are unable to stop thermal runaway on its own. Although containment bags are crucial, they should actually be used as a last resort rather than as a first line of defense in a thermal runaway scenario. Julie Kozma, a seasoned flight attendant, stated that the unit must first be cooled down. In a March 2023 advisory, the FAA states that while it recognizes the worth of these products, “no FAA test standards exist for these containment products nor does the FAA have a mechanism in place for the approval of these products.”
Why are these occurrences increasing? One explanation is the sheer volume of gadgets: on a normal flight, hundreds of lithium-ion cells may be found in the cabin, and the average traveler brings four rechargeable devices on board. The widespread use of inexpensive, uncertified, or fake batteries and chargers which lack essential safety features like short-circuit and overcharge protection is another contributing factor. According to retired airline pilot John Cox, “You can buy one on the streets of New York for five bucks, but the likelihood of that [charger] creating a battery overheat is significantly higher.”
Industry norms are changing. Devices that want to be certified by UL (UL 2056 for power banks, for example) must adhere to strict safety standards, which include safeguards against short circuits and overcharging. According to UL Standards & Engagement, the recently released UL 5800 standard provides performance criteria for products used by flight crews to suppress and contain thermal runaway incidents. It specifically addresses fire containment products for lithium-ion batteries on aircraft.
Travelers’ awareness is still low, though. According to a recent UL survey, over three-quarters of Americans do not remember seeing battery safety warnings during check-in, and 44% of Americans know nothing about lithium-ion batteries. According to survey data, 27% of travelers in 2023 reported putting power banks and spare lithium batteries in their checked luggage, despite the FAA’s explicit directive that these items should be carried in the cabin rather than checked luggage.
The message is clear for frequent flyers and tech-savvy tourists: select approved devices, keep them visible, and follow airline policies. The next lithium-ion incident is not a question of if, but when, as demonstrated by Southwest’s experience. From visible-use regulations to containment standards, the regulatory environment is changing to reflect the understanding that technology and awareness must develop simultaneously to ensure the safety of the skies.
