Announcing the cancellation of the flights, the Indian carrier wrote on X: "Due to a significant power outage, London Heathrow Airport has been shut down until 23:59 on 21st March. All Air India flights to and from London Heathrow for 21st March have been cancelled."

"For more information or assistance, please call our Contact Centre at +91 1169329333 / +91 1169329999. UK-bound customers, please call +44 203 757 2760," the airline said.

Gatwick Maintains Normal Operation

Meanwhile, Gatwick Airport, which also serves London, said it is maintaining normal operations.

"We are aware of the situation at @HeathrowAirport today and are supporting where required," the airport wrote on X.

"Flights from London Gatwick are operating as normal today," it said.

Heathrow Asks Travellers To Avoid

London's Heathrow Airport was shut down till midnight on Friday after a massive fire broke out at a nearby substation which supplies electricity to it.

Alerting passengers, the Airport wrote on X: "Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage."

The airport authority further said: "To maintain the safety of our passengers and colleagues, Heathrow will be closed until 23h59 on 21 March. ."

The airport directed passengers not to travel to the facility and contact airlines for information on their flights.

"We apologise for the inconvenience," the X post said.

Staff Working To Solve

"Whilst fire crews are responding to the incident, we do not have clarity on when power may be reliably restored," a Heathrow spokesperson told BBC, adding that staff were "working as hard as possible to resolve the situation".

Hayes Substation Fire

Located in Hayes town in West London, the fire that broke out at the substation left thousands of homes without power.

Also Read: Massive fire breaks out at London electric substation, Heathrow Airport closed

According to local media reports, authorities have evacuated 150 people from properties located close to the substation.

Ten Fire Engines Operating

London Fire Brigade said ten fire engines and around 70 firefighters are working to douse the flame.

According to British media reports, over  16,300 homes are suffering power outages following the fire incident.

Energy supplier Scottish and Southern Electricity Networks wrote on X: "There’s a fire at North Hyde substation in West London and emergency services are in attendance."

Meanwhile, the cause of the fire is still not known.