London’s Heathrow Airport was closed for all of Friday, shutting down one of the world’s busiest airports and causing worldwide travel disruptions after it lost power because of a fire nearby.

The closure disrupts an important travel hub for Britain, Europe and the world. Daily, an average of more than 220,000 passengers traveled through the airport last year on flights offered by 90 airlines to more than 180 destinations around the globe.

On Friday morning, planes were scheduled to arrive from as far away as Vietnam, India and Brunei, and passengers were expecting to take off for destinations like Tokyo, New York and Riyadh.

Heathrow advised passengers not to travel to the airport because it would be closed until at least 11:59 p.m. local time.

Here is what we know about Heathrow’s closure.

The problem began with a nearby fire.

Heathrow said early Friday that it had been hit by a power outage, caused by a fire at an electrical substation supplying the airport.

The London Fire Brigade said that it had been called to the fire in western London late Thursday, deploying dozens of firefighters. About 150 people were evacuated from the area.

The cause of the fire was not known, the fire brigade said.

Nearby homes and businesses were also affected, the fire brigade said. About 16,000 customers were without power early Friday, according to Scottish and Southern Electricity Networks, a British energy company.

Ripple effects will be global.

Heathrow’s closure will affect at least 1,351 flights in and out of the airport, according to Flightradar24, a flight tracking website. As the closure was announced early Friday, 120 aircraft that had been scheduled to arrive at Heathrow were in the air.

Some were diverted to alternate airports, including London Gatwick Airport, Amsterdam Airport Schiphol and Charles de Gaulle Airport in Paris, Flightradar24 said. Others began returning to their origins.

The disruption caused by the fire was expected to spread into Friday morning, said Pat Goulbourne, assistant commissioner at the fire brigade.

“We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens,” a Heathrow spokesperson said in a statement.

Britain’s laws protect many travelers facing disruptions.

Airlines are required to look after you if you are departing from Britain on any airline or arriving there on an E.U. or U.K. airline. If your flight is canceled, you should be offered a choice of a refund or alternate travel arrangements at the earliest opportunity, according to Britain’s Civil Aviation Authority.

If you choose to travel at another time, they must provide you with a reasonable amount of food or drink, accommodation if you are rerouted the next day and transport to and from the accommodation.

If your flight has been canceled or diverted, check your airline for its policies.