What happens if airports lose power?

An airport doesn't depend on a single power supply. Facilities of a certain size receive power through two independent lines and, beneath that, keep diesel generators able to take on the essential load within seconds. Between the power cut and the generator start-up, uninterruptible power supply systems kick in — batteries that keep equipment that cannot tolerate even a flicker running without any interruption.

Annex 14 of the Convention on International Civil Aviation sets maximum switchover times for visual aids. On runways with Category II and III precision approaches, the lighting restoration time must be one second or less; less demanding configurations allow up to fifteen seconds. Air traffic control, radio navigation aids and communications have their own backup.

The problem with an extended blackout usually isn't the runway, but everything else. Check-in and boarding systems, baggage belts, security checkpoints, boarding bridges, jet bridges and fuel supply run on the general grid and aren't always on the emergency circuit. Without them, passengers can't be processed, even if a plane could technically take off.

When a major airport reduces its capacity, the entire network feels it. Flights en route to it divert to alternates, crews run out of their maximum duty time while waiting, and aircraft end up out of position for the next day's rotations. That's why recovery after a prolonged outage usually takes much longer than the blackout itself: restoring power is a matter of hours; repositioning the fleet, a matter of days.