ATLANTA (AP) — Georgia Power’s top executive apologized for the power outage that crippled Atlanta’s airport, saying he realized that it inconvenienced thousands of people.

CEO Paul Bowers said in a phone interview Monday that a switch gear failed, causing a fire that then spread to cables coming in from two substations. But he said it wasn’t clear what caused the switch gear to fail.

Bowers said failures are very rare, but now that they’ve had one, they have to figure out what to do about it going forward. He said they will look at ways to isolate the switch gear and cables from each other, possibly by encasing one or the other in concrete.

He said the fire happened in a service tunnel deep under the airport, so it never posed a danger to anyone.