A single personal electronic device with a lithium battery that overheats and catches fire in the cargo hold could potentially down a commercial airliner. That’s what the US Federal Aviation Administration found in its latest research. Regulators had originally thought that the fire suppressant systems in cargo holds would be able to extinguish flames if they were to arise from an overheated lithium-battery-operated device. However, the most recent study has shown that the systems don’t actually have the power to put out the flames caused by an overheated lithium battery, commonly found in laptops, cell phones and a wide range of other devices, when combined with other flammable substances, such as gas in an aerosol can or cosmetics. “That could then cause an issue that would compromise the aircraft,” said Duane Pfund, international program coordinator at the US Pipeline and Hazardous Materials Safety Administration. The FAA forbids passengers from checking spare (uninstalled) lithium metal batteries, requiring them to be carried on. In addition, the FAA says that “all spare lithium batteries must be removed from the bag and kept with the passenger in the aircraft cabin,” when a carry-on bag is gate checked. Lithium batteries are a type of rechargeable battery most commonly found in cell phones and laptops. Carrying them on board and in carry-on luggage doesn’t pose the same threat as if they were to be checked in the cargo hold. In the hold, bags — and therefore the potential fire — is not reachable, however, experience has shown that they can be extinguished with water, according to Bloomberg, and therefore, they’re more safe when flying in the cabin. Bulk shipments of rechargeable lithium batteries are banned from passenger planes. However, the FAA hasn’t imposed any new restrictions on what passengers are allowed to check in their bags. In a notice to airlines in 2017, the FAA said they should consider conducting safety checks to determine what else could be done to prevent battery fires in the cargo hold. “One way or another, we have to deal with these hazards,” said Scott Schwartz, director of the Air Line Pilots Association’s hazardous goods program. The last few years have seen a string of incidents with batteries exploding in aircraft or near airports — including on a Delta aircraft, in a TSA checkpoint line and China Southern flight.