Heathrow executives are defending their response to a fire that shut down Europe’s busiest air hub for almost a day.

Heathrow’s chief executive has defended the airport’s response to the power outage and shutdown that sparked global travel chaos, apologizing to stranded passengers and confirming the airport is “operating as normal” Saturday.

London’s Heathrow Airport closed on Friday after a fire at a nearby electrical substation, resulting in hundreds of flight cancellations.