With jet-powered Geran drones now slipping through Ukrainian air defences, Russia’s war factories are building a mass drone arsenal that could soon put EU governments and energy grids in a permanent crisis mode.

As Russia scales up production of its jet-powered drones — the Geran-4 and Geran-5 — Ukraine is struggling to shoot them down amid prolonged waves of attacks.

Russia has dramatically intensified its air war over Ukraine, launching more than 2,500 jet-powered Shaheds in August alone, according to Ukrainian officials. That compares with…