An aviation safety expert says that fires caused by lithium ion batteries are the new risk faced by airlines … and is here to stay.

Retired airline captain John Cox says massive strides have been made in terms of fire safety on board planes but the battery risk is a new challenge.

And he says there are several instances every year where fires on board planes are caused by batteries overheating in personal electronic devices.

He reveals how airlines have learned vital lessons from previous fire hazards and consequently have vastly improved fire safety on board.

Mr Cox says an air tragedy in 1983 claimed several lives when a passenger plane with a fire in a lavatory made an emergency landing but when the doors and exits were opened there was a deadly flashover.

It emerged the interior panels and seat covers were not fire resistant like they are today and within five years all airliners had fire-blocking material for seat covers, smoke detectors in lavatories and low level lighting to help people escape if the cabin was filled with smoke.

These improvements helped reduce the likelihood and severity of a fire, but in 1998 a passenger plane cruising from New York to Geneva suffered an electrical fire that spread into the insulation overhead. The fire expanded quickly, causing control of the jetliner to be lost. All on board died.

Writing for USA Today, Mr Cox, who runs his own aviation safety consulting company, Safety Operating Systems, said: “Investigators found serious deficiencies in the insulation certification process and manufacturing. In addition, they found wiring insulation failures and improper installation of in-flight systems. The investigation resulted in improvements in testing standards for aircraft insulation, wire insulation and how new equipment is installed.

“Several changes have been made since then to increase safety. Modern jets have much-improved insulation in the cabin, wiring insulation that is more resistant to cracking or burning and improved wiring maintenance programmes. All of the interior panels are made of high fire-resistant material that does not emit toxic smoke when exposed to fire. Modern seats are stronger and the covers are made of fire-blocking material.

“Crew members are better trained to act as firefighters and provided with better fire extinguishers. Early detection leads to early action before the fire can spread. Consequently, in-flight fire no longer is a major cause of accidents.”

But he warns: “Today, a new fire risk is rising - lithium batteries brought on board by passengers. Globally, airlines experience a lithium battery fire multiple times a year. Special training and equipment are needed to deal with lithium battery fires.

“Airlines and regulators are dealing with the growing threat. More will be done to effectively deal with lithium battery fires but this issue will be with us for the foreseeable future.”

* AvSax fire containment bags are now on board several major airlines worldwide and were deployed 27 times in 2017.

If an electronic device starts to seriously overheat or emit smoke the cabin crew will pour at least two litres of water into an AvSax. It is imperative to first knock down the flames from the device using an on board halon fire extinguisher, then transfer the device into AvSax before it reignites. Additional water is then required. The water activates the polymer gel inside the bag causing it to expand around the device. Should the device keep on venting then the AvSax is tough enough to absorb the energy.

The AvSax cools the batteries in the device, reducing the likelihood of the battery igniting but if it does go into thermal runaway it is all contained within the bag.

Amazingly, the water is absorbed into the internal lining of the bag so the device is dry when it is removed.