Heathrow Airport in London is slowly resuming operations Friday afternoon, but passengers flying out of Boston should check with their airlines before heading to Logan International Airport, officials said.
Flights to and from Heathrow were canceled Friday after a fire at a nearby substation knocked out power to Europe’s busiest airport, snarling travel plans for hundreds of thousands of people worldwide.
Around 12:15 p.m. Friday (4:15 p.m. London time) Heathrow posted on social media that power had been restored and limited flight operations would resume Friday. Full operation is planned to resume Saturday.
“Our teams have worked tirelessly since the incident to ensure a speedy recovery. We’re now safely able to restart flights, prioritising repatriation and relocation of aircraft,” airport operators wrote on social media. “Please do not travel to the airport unless your airline has advised you to do so.”
The airport also said that “we hope to run a full operation tomorrow and will provide further information shortly. Our priority remains the safety of our passengers and those working at the airport.”
Massport spokeswoman Jennifer Mehigan wrote earlier Friday that the situation in London is fluid.
”Passengers should check with their airlines for the status of their flight before coming to the airport," she wrote.
According to the Massport flight schedule site, a handful of flights scheduled this evening for Heathrow are scheduled to depart on time. One British Airways flight for Friday night is canceled.
About seven flights depart for Heathrow from Logan daily, Mehigan said.
Across the world, at least 1,350 flights to and from Heathrow were affected, flight tracking service FlightRadar 24 said. The impact is likely to last several days as passengers try to reschedule their travel and airlines work to get planes and crew to the right places.
The fire, at an electrical substation about two miles from the airport, knocked out power to Heathrow just before midnight on Thursday.
The “significant power outage” forced officials to shut down the airport temporarily “to maintain the safety of our passengers and colleagues.”
Energy Secretary Ed Miliband said the “catastrophic” fire also appeared to have knocked out a backup generator.
The cause is under investigation, and officials said there was “no suggestion” of foul play.
Material from the Associated Press was used in this report. This is a developing story and will be updated.
John R. Ellement can be reached at john.ellement@globe.com. Follow him @JREbosglobe.