London’s Heathrow Airport, one of the world’s busiest aviation hubs, has been fully shut down following a major power outage caused by a massive fire in the surrounding area.

The closure is expected to disrupt more than 1,300 flights, affecting tens of thousands of travelers worldwide.

Airport authorities have urged passengers to stay away, warning of “significant disruption” expected to last for days. According to flight analytics firm Cirium, as many as 145,000 passengers could face delays or cancellations, with flight diversions already taking place across Europe and North America.

The London Fire Brigade called the blaze a “prolonged incident”, with investigations still underway to determine the cause. In the meantime, 36 inbound flights have already been rerouted, while some planes were forced to return to their original airports.

The shutdown’s effects are being felt globally, with flights from cities including New York, Singapore, and Perth among those impacted.

Travel experts warn that the backlog of grounded or redirected flights could take several days to resolve, resulting in widespread travel chaos across international air routes.