All Flights at London’s Heathrow Airport were grounded for the entire day on Friday after a pair of explosions at a nearby electrical substation left the major European travel hub in chaos.

Nearly 1,400 flights to and from the airport have already been affected, including 120 that were already in the air, according to a report from BBC News. Many more flights are expected to be cancelled as the airport will be shut for the remainder of the day.

Nearly 5,000 homes in the region are also without power after two explosions ignited a blaze at a substation located at Hayes, west London. Heathrow officials have warned of a “significant disruption” for the airport, which often serves as a connection hub for flights from America to other destinations across Europe and beyond.

“Due to a fire at an electrical substation supplying the airport, Heathrow is experiencing a significant power outage. To maintain the safety of our passengers and colleagues, Heathrow will be closed until 23h59 on 21 March,” reads a statement posted to the airport’s X account. “Passengers are advised not to travel to the airport and should contact their airline for further information. We apologise for the inconvenience.”

Counterterrorism police are currently seeking a cause of the fire looking into the possibility of sabotage, according to the Times of London. While there are no immediate signs of foul play, the measure is precautionary due to fears of active Russian sabotage operations in the United Kingdom and across Europe. Multiple incidents across the continent have been carried out by Russian agents in recent years, including a warehouse fire at London.

Heathrow is one of the busiest airports on the planet, with nearly 84 million passengers going through the airport in 2024 alone.