Plane safety due to lithium battery fires in the cargo hold

Question

I stumbled across an article saying that one faulty laptop in the hold (e.g. from gate-checked hand luggage) can bring a plane down (lithium batteries). I have 3 questions:

• Why is halon gas used as a fire suppressant as it can‘t extinguish lithium batteries? (Apparently only cardboard and clothing)
• How long can a commercial passenger plane contain a fire in the cargo?
• In this case of emergency, how quickly can a pilot land a plane from 40,000 ft? I‘m hoping the third answer is quicker than the second.

I just want to feel safe when I travel.

Answer 1

I'm a frequent flyer (2M+ miles flown) and I have never encountered a situation that was worrisome or made me uncomfortable.

Here are some US statistics that may help you:

1. The number of lithium battery incidents in 2023 was 75. Compare that to about 16 million flights: the likelihood to have an incident on your flight is about one in 200,000.
2. That is "incidents". No incident resulted in a fatality. In fact the number of fatality per 100 million passengers on board in 2021 & 2022 was zero (down from 0.9 in 2020). 2023 wasn't easily available.
3. The number one reason for fatalities on airplane is "natural death" caused by a medical issues. People do die, and occasionally it happens on a plane.
4. Worldwide, air travel safety is still improving with 2023 being the "safest" year ever. See for example: https://www.iata.org/en/pressroom/2024-releases/2024-02-28-01/#:~:text=There%20were%20no%20hull%20losses,aircraft%2C%20resulting%20in%2072%20fatalities.

I chose the US simply because the data is well documented and easy to come by. However, this is representative for most other countries as well.

From the IATA world wide report:

The fatality risk improved to 0.03 in 2023 from 0.11 in 2022 and 0.11 for the five years, 2019-2023. At this level of safety, on average a person would have to travel by air every day for 103,239 years to experience a fatal accident.

Nothing is truly safe, but air travel is by far the safest mode of travel. The most dangerous part of your journey will be the transport to and from the airport. Flying commercially, itself, is extremely safe.

Answer 2

Chemist here, not much of an aviation expert.

Batteries are energy sources and as such, all types of them do have unpleasant failure modes related to uncontrolled release of the stored energy.

What makes Li-Ion batteries different?

1. They have very high energy density, making them useful in many use cases where e.g. NiMH or lead-acid cells will not do. This leads us to:
2. They are everywhere. Before the dawn of the Lithium era, few people carried battery-powered devices. The devices were expensive, bulky, had limited battery run and whoever carried them had a very good reason for this.
3. They require precise electronics to keep them safe. The battery management electronic circuits embedded in every battery have their own failure modes.
4. Their electrolyte is not water-based. In earlier battery technologies, the battery water content was significant and this, together with their lower energy density, limited the battery ability to produce high temperatures, capable of igniting nearby objects. In the general case, the Li cell electrolyte is somewhat flammable itself.

In short, Li batteries can sometimes self-ignite and in very rare cases, explode. When they self-ignite, they usually burn like a firework, throwing flames and seeding sparks around. The whole show spans over 1-10 seconds.

The firework-like burning is not controllable with the usual firefighting methods (e.g. powder or foam) because the process does not use air in the first place. Water is the right thing to use.

On the other hand, the damage is limited by the battery size. A phone battery can cause very bad skin burns, but is hardly capable of starting a fire, even if one really needs to.

What is done in airplanes, to mitigate these risks?

The most important: Airlines limit the size of the batteries. One is not allowed to bring a battery of more than 100 watt-hours on an airplane. This amounts to a very large laptop battery or a very large USB battery bank.

A 100 watt-hour Li battery is not capable of explosion strong enough to destroy a vital plane structural element or system.

The worst it can do is to ignite some combustible material nearby.

If uncontrolled, an airplane fire is a recipe for a problem, but this is what the fire supression systems in the cargo rooms are for.

The limited size of the batteries and the halon system together really do solve the problem.

The fire gets completely extinguished instead of just contained.

If the bad thing happens in the passenger cabin, the cabin crew is trained to deal with the problem as well.

In order to bring an airplane down by a Li battery, one needs at least 30kg battery of fairly low quality.

This is really hard to check in unnoticed and even harder to carry by hand.

Even then, a big Li batteries are usually made of small cells and it requires as much as a car crash to make many of them go off at once.

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In regard to landing a plane from 40000ft:

Ever tried to stop a car running at a highway speed in emergency? If you are a very good driver and the car is in top condition, you need something like 10 seconds. If the car catches fire for some reason, by the time it stops it usually burns hard and the only viable strategy is to get out as quickly as possible.

In an airplane cruising at 40000ft, an emergency landing can take as little as 20 minutes if a clear runway is available just at the right distance ahead or e.g. 2 or 3 hours if you are crossing the ocean.

This is why airplanes are made (and organized!) to limit the emergencies possible and to deal with them onboard.

Answer 3

Entertaining your questions will not make your fears go away, in fact, answering them will only make you come up with more illogical questions and so on, and your fear will grow and grow. It's like when you search for sickness symptoms online, you will always hit that "cancer" answer and then when you visit the doctor, it's just a pimple.

The doctor in this case is the statistics, which clearly proves that planes are the safest method of transportation.

However, I'd suggest one of the following:

• Travel using another transportation method that you are more comfortable with.
• Go see a specialist, some pills before the flight can help. There are some Aerophobia courses that might help you as well.
• Believe the statistics made by professionals and stop the self-researching.

Answer 4

Why is halon gas used as a fire suppressant as it can‘t extinguish lithium batteries? (Apparently only cardboard and clothing)

Because essentially nothing other than completely burying it in sand can extinguish an active metal fire reliably, and this is doubly true of lithium fires (lithium can even burn in an atmosphere of pure nitrogen or pure carbon dioxide). Halon covers essentially everything else that is likely to happen in the hold.

How long can a commercial passenger plane contain a fire in the cargo?

Indeterminate, because as far as I can tell there are no recorded cases of a lithium battery fire in the hold of a commercial passenger jet aircraft. The only case I’m aware of of an actual lithium battery fire in the hold in any aircraft was a cargo jet, and that was a major issue mostly because it was a whole pallet of lithium batteries that caught fire.

Because airlines are very particular about people not having lithium ion batteries in checked luggage, they are rarely, if ever, in the hold of a commercial passenger aircraft.

There are some incidents of such fires in the cabin, but those are generally far more manageable because they are almost always discovered before they become a major issue.

In this case of emergency, how quickly can a pilot land a plane from 40,000 ft? I‘m hoping the third answer is quicker than the second.

Where in the world, and what airframe?

For something really big, like an A380, it may easily be multiple hours, because you need to find somewhere that you can actually land the aircraft (an A380 needs at minimum 2150m of runway for safe landing). For something small, like a CRJ100, it’s easier, but still requires finding somewhere to land.

And the reality is, the finding somewhere to land part is often the longest step in a case like this. Most passenger aircraft can (reasonably safely) descend fairly quickly if they need to, but it’s not much use unless you can actually get on the ground (or the surface of the water) safely.

Answer 5

This is likely not going to happen if the ground staff is trained correctly, because you should be asked to remove the devices containing the batteries from the luggage going into the hold:

Lithium batteries, which power everyday devices, can catch fire if damaged or if battery terminals are short-circuited.

Devices containing lithium metal batteries or lithium ion batteries, including – but not limited to – smartphones, tablets, cameras and laptops, should be kept in carry-on baggage. If these devices are packed in checked baggage, they should be turned completely off, protected from accidental activation and packed so they are protected from damage. Requirements vary based on the type of device and size of battery.

Spare (uninstalled) lithium metal batteries and lithium ion batteries, portable rechargers, electronic cigarettes and vaping devices are prohibited in checked baggage. They must be carried with the passenger in carry-on baggage. Smoke and fire incidents involving lithium batteries can be mitigated by the cabin crew and passengers inside the aircraft cabin.

If carry-on baggage is checked at the gate or planeside, spare lithium batteries, electronic cigarettes, and vaping devices must be removed from the baggage and kept with the passenger in the aircraft cabin. Even in carry-on baggage, these items should be protected from damage, accidental activation and short circuits. Battery terminals should be protected by manufacturer’s packaging or covered with tape and placed in separate bags to prevent short circuits.

Damaged, defective or recalled lithium batteries must not be carried in carry-on or checked baggage if they are likely to be a safety concern by overheating or catching on fire.

When in doubt, leave it out.

For me this would also lead to leave out a laptop if it is not well protected by the backpack or whatever it is in.

Source with a link to a more detailed description: https://www.faa.gov/newsroom/lithium-batteries-baggage

And a list of the incidents with description the FAA is aware of (476 between March 2006 and March 2024): https://explore.dot.gov/t/FAA/views/LithiumBatteries/IncidentDetails?%3Aembed=y&%3AisGuestRedirectFromVizportal=y

Maybe reading how these cases were professionally handled helps to reassure you.

I can't say how many flights the FAA was tracking, but there are millions of flights each year, so the number of incidents concerning lithium ion batteries per flight is in the order of a few per million.