I suspect the increasing number of airborne fires is mainly due to the increasing number of passengers carrying devices that use lithium-based batteries. Both the physical number of devices and the battery capacity of those devices is increasing. As recently as 2015, almost no one carried a rechargeable “brick” with them for portable recharging. Now they seem to be everywhere and I question the quality control of something made in a sweat shop in some third world country. What really scares me is that, sooner or later, someone will pack one in a suitcase that ends up in the baggage hold and cooks off down there. At least in the cabin the device can be put in a fireproof bag and contained.