Lithium battery fires or thermal runaway incidents are becoming a very common occurrence on aircraft, with figures globally estimating one or two events every week. These emergencies usually involve overheating, smoking, or flaming batteries and frequently result in flight disruptions. With more personal devices than ever before being carried that contain the batteries, the chance of such events increases.

In recent years, there has been more emphasis on these during safety training for flight crew and flight attendants who undergo fire training. US carriers have realized that screen-based recurrent training cannot prepare crews for the lithium-battery threat that now hits aircraft twice a week. Delta Air Lines is one such carrier that has recognized that this is a growing problem and invested in its cabin fire safety training, which the FAA and the industry safety groups now track as a top-tier cabin hazard.

Cabin Fire Safety Training

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Delta Air Lines ordered four new fire trainers from Flame Aviation that simulate real in-flight fire scenarios, including thermal runway events involving lithium-ion batteries. Delta ordered two V7000 Brigade units for its Atlanta facility and two further V9000 Commander units for its new pilot training center in Salt Lake City. Deliveries of the trainers are expected in Q1 and Q2 of 2027, after Delta commissioned them two years ago in response to the increasing number of on-aircraft lithium battery incidents, according to a report at evrimagaci.org.

Delta previously commissioned a V9000 Commander trainer and opened a massive 50,000-square-foot pilot training facility in Salt Lake City in December 2024. The airline invested in the state-of-the-art facility, the first significant pilot training center outside of Atlanta, where its first training center opened at its headquarters in 1968. The new training facility will host over 1,000 training events every month and cater to training in Delta’s western hubs, including flight attendant training.

Lithium-ion battery fires are an escalating threat in aviation, with thermal runaway incidents occurring at an average rate of two per week in 2024, with 18% of onboard incidents resulting in a diversion, returning to the gate, or an emergency evacuation, according to information at ulse.org. The same report says that 89% of thermal runaway incidents occur on the aircraft, and 52% happen during the cruising phase. In 2024, the FAA verified 89 lithium battery incidents involving smoke, fire, or extreme heat on passenger and cargo aircraft in a single year, according to faa.gov.

Thermal Runway Incidents

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Contributing to Delta’s decision to rethink crew training and how to tackle lithium battery fires were numerous incidents. A recent Delta Air Lines flight was diverted to Charlotte due to a ‘mysterious odor’ in the cockpit. The flight from Orlando to Detroit declared an emergency when an unusual smell was detected and diverted. The aircraft was evaluated and inspected, but no cause of the odor was disclosed. The flight continued to Detroit the following day, as reported to the Grand Pinnacle Tribune.

In July 2025, a Delta flight diverted to Fort Myers, Florida, due to a battery fire in a passenger’s backpack. The incident occurred on a flight from Atlanta to Fort Lauderdale, and the flight attendants worked quickly to extinguish the fire. The crew reported smoke in the cabin, and the flight crew followed procedures for an emergency landing. The backpack was put in a containment bag and isolated until landing once the fire had been extinguished, according to Viet Flight Training.

In October 2025, an Air China flight traveling from Hangzhou to Seoul had to divert due to a lithium battery fire onboard. An article at AVD Fire explains that the lithium-ion battery self-ignited in a passenger’s carry-on bag in an overhead compartment. There were visible flames and smoke in the cabin. The crew followed emergency procedures and diverted to Shanghai. Prior to that, in January, an Air Busan aircraft was destroyed on the ground. According to ULSE, there was a catastrophic power bank fire caused by thermal runaway, and the aircraft was evacuated.

Improved Fire Training

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The timing of Delta’s investment in fire training is notable, given the increased focus on in-flight safety. Fire trainers are designed to simulate a range of in-flight fire scenarios, including the increasingly common threat posed by lithium-ion battery fires in overhead luggage compartments. Fires in seats, lavatories, and the galley can also be recreated to help flight attendants hone their firefighting skills. Delta is ensuring that its crew have access to the latest fire-training facilities and are prepared for any eventuality, such as an onboard fire.

These realistic training simulators allow all flight crew to practice responding to emergencies in a controlled environment, practicing their skills for scenarios that, whilst rare, can escalate quickly if not managed quickly and calmly. Delta is not alone in this pursuit, with other US airlines like American Airlines, JetBlue, and SkyWest Airlines also investing in similar fire training equipment, enabling their crew to be able to deal with possible fires and increasing numbers of thermal runaway incidents.

Flight attendants are required to handle firefighting equipment every year at their recurrent training. This includes donning the smoke hood or protective breathing equipment (PBE) and using a fire extinguisher. Every three years, flight attendants are required to participate in practical scenarios in a fire trainer with real fire, fire extinguishers, and smoke hoods to accurately emulate possible fires on board. Flight crew also have to complete extensive fire training.

What Is Thermal Runaway?

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Rechargeable devices such as phones, laptops, tablets, and power banks are essential items these days, and most passengers carry multiple devices. These contain lithium-ion batteries and have proven to be a safety risk in aviation, and things can get very complicated at 34,000 feet. If they are damaged, improperly charged, poorly manufactured, or counterfeit, lithium-ion batteries can enter thermal runaway, when batteries overheat and can create a fire or an explosion.

Lithium-ion battery fires burn with intense speed and heat, potentially causing significant and widespread damage within seconds. They can also be more challenging to extinguish compared to fires involving other materials. According to a report by ULSE, two in five passengers are packing rechargeable devices in checked luggage, which cannot be accessed during the flight. 52% of US passengers are more concerned about other people’s devices than their own.

The report also shows that half of all Americans admit they don’t know about lithium-ion batteries, and that 60% were not aware that their devices contain them. Almost all passengers bring at least one device on board, with most bringing four, the most common being the smartphone. Vapes are the leading cause of thermal runaway incidents at 28%. Passengers surveyed admitted that they sometimes pack their devices in their checked baggage.

How To Deal With Incidents

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If there is a lithium-ion battery fire, move people away from the area, although this is difficult in areas such as on an aircraft. If the device is small, like a phone, tablet, or laptop, it can be dropped in a bucket of water; in the case of an aircraft, an ice bucket or waste bin may be used. The item may start by hissing, smoking, or developing small flames, and there may be an acrid chemical smell. If safe to do so, the item should be switched off or unplugged. A standard fire extinguisher may be used to put out the fire, but it will not stop the device from overheating, according to Airbus.

How do flight attendants deal with fires on board? The first crew member at the scene becomes the ‘firefighter’ and begins fighting the fire.

They need a fire extinguisher, fire gloves, and a smoke hood. The second crew member becomes the communicator, informs the flight crew, and keeps them updated on the situation. The third crew member becomes the collector and gets back up fire extinguishers and equipment. The firefighter and collector can then rotate in putting out the fire as necessary. Any remaining crew can move passengers away from the area and manage them assertively.

The flight crew will divert the aircraft to the nearest suitable airport for safety reasons. In the meantime, once the fire is out, the crew can douse the device in water or non-alcoholic liquids and place it in a fire containment bag, if available. The firefighters should monitor the device in case it reignites and have water and a fire extinguisher available. The remaining crew needed to secure the cabin ready for landing.

Key Points

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Cell phones, tablets, and e-cigarettes are all part of modern life, but they also pose a risk to aviation safety. Thermal runaway incidents are becoming more common, which is why airlines like Delta Air Lines are investing in fire-training simulators to train their crews. When lithium-ion batteries overheat, they can cause a fire, toxic smoke, or an explosion, which in an aircraft in cruise is a very dangerous situation.

The European Union Aviation Safety Agency (EASA) strongly recommends carrying these lithium-battery-powered items, such as power banks and e-cigarettes, in the cabin so that cabin crew can react quickly should a thermal runaway occur. They also recommend that flight and cabin crew be trained specifically to put out lithium battery fires quickly, efficiently, and safely.

Passengers should be informed about the risks of carrying lithium batteries or devices powered by them, and about the restrictions on their use on an aircraft. Always keep portable chargers (power banks) and spare batteries in your cabin baggage. Cargo holds are harder to access, making battery fires in the hold far more dangerous. Do not charge your devices using personal power banks while in flight; only use the airline’s provided seat power. Onboard the aircraft, if a passenger drops their phone between seats, it is important to contact a crew member immediately.