A simple piece of tech vital for keeping modern devices running could spell disaster on flights, experts have warned. It’s likely whenever anyone boards a plane these days they are probably carrying at least a mobile phone, but also perhaps a tablet and laptop, as well as a host of other electronic equipment.

Most technology these days is powered by simple rechargeable batteries, which make it easy to power up devices again and again. But the substance that forms these batteries, lithium-ion, is also highly unstable if it is faulty or damaged. When lithium-ion batteries go wrong they can explode after entering a state known as thermal runaway, which means they can heat up to temperatures reaching 900C. As well as searing temperatures, the resulting fires on the batteries can produce harmful toxic clouds of gas.

Commercial airlines are increasingly vigilant to the threat of the power packs after a series of incidents on board aircraft in recent years, including a terrifying incident on an Air France flight from Paris to Accra, in Ghana. Following a series of blazes ignited by the batteries during flights, most airlines now do no allow the lithium-ion packs to be checked in with hold baggage. 

Keith Tonkin, the boss of the Australian consultancy Aviation Projects, told the New York Times it was better to have the devices with passengers in the cabin rather than store them in a part of the aircraft no one could reach. 

He said: “If there is a fire, you’d rather have it in the cabin than checked baggage, and you’d rather have it closer to a person rather than in the overhead bin, where it’s more difficult to get it out and manage the fire.”

Hong Kong aviation expert Warren Chim Wing-nin said it was important passengers follow the rules when airlines ask them not to put lithium-ion power packs in their hold luggage, and he warned against buying cheaper potentially less robust products. 

“If it’s not a good product, the risk will be much higher,” he told the South China Morning Post.

British Airways, Ryanair, and Jet2 already have firm policies regarding where and how passengers can transport power banks.

Most airlines do not allow power banks or spare lithium-ion batteries to be placed in checked luggage due to the risk of fire. The International Civil Aviation Organization banned them from cargo holds on passenger planes in 2016.

British Airways prohibits all battery-powered devices from being stored in checked baggage and requires passengers to carry them in hand luggage. The airline also advises that devices must be packed to prevent accidental activation, while damaged batteries are banned completely.

Ryanair follows similar guidelines, stating that power banks must be kept in carry-on bags. Jet2 allows passengers to carry up to 20 spare lithium batteries, including power banks, but requires each battery to be individually protected to prevent short circuits.