A passenger’s iPad caught fire as a plane was flying to London from the USA … and it has been classed as a serious incident by investigators.

According the Aviation Herald the jet was on its way from Los Angeles to London Heathrow in early April when the device suddenly caught fire.

Cabin crew managed to extinguish the fire, cool the device down and secure it. The aircraft continued the journey to London for a safe landing.

The Air Accidents Investigation Branch officially reported "passenger iPad caught fire; extinguished by cabin crew," rated it as a serious incident and opened an investigation.

* AvSax fire containment bags (pictured) 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.