Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

Spain suffered several power glitches and industry officials sounded repeated warnings about the instability of its power grid in the build up to its catastrophic blackout on Monday. The government has ordered several investigations into the blackout.

One of Europe’s most severe blackouts grounded flights, paralyzed metro systems, disrupted mobile communications and shut down ATMs across the Iberian Peninsula.