Portuguese grid operator REN will allow utilities to resume imports of electricity from Spain, but the transmission capacity will be limited to around one-third of the levels seen before the huge power blackout in the two countries on April 28.

Whatever the root cause, one thing’s crystal clear: major blackouts don’t just switch off the lights; they send shockwaves through global supply chains.

Alanna Gladstone, a 40-year-old film editor, had landed in Portugal’s capital, Lisbon, on a flight from New York hours before the outage. She checked into her Airbnb and took a nap; by the time she woke up, the technology that the country takes for granted had gone dark.