Heathrow Airport closure may cost airlines hundreds of millions of dollars — and could have been even worse.

• Heathrow Airport shut down due to a fire, disrupting flights for most of the day.
• The shutdown affected thousands of passengers and likely cost airlines millions in rerouting.
• Airlines could lose $80 to $100 million rerouting passengers and any accommodation.

London Heathrow Airport closed on Friday due to a power outage, crippling flights into the region for the better part of a day. The fallout will cost airlines a pretty penny — but the timing could have been much worse.

Thousands of passengers expecting to be in London spent hours in the air only to end up back in places like Tokyo, Mumbai, and Dallas. Australia's flag carrier Qantas said its passengers who were diverted to Paris would be transported to London via bus, a nine-hour journey.

Heathrow said it would re-start flights late Friday, meaning some travelers could get back on track sooner than expected. But reorganizing an airline network is no easy task when diversions and cancellations leave planes and crew in unexpected places.

Luckily for Heathrow and the airlines that call it home, especially British Airways, the power outage was fixed in less than a day and did not occur during a crowded travel time, like the summer holidays.

Over the years, natural disasters and infrastructure problems have grounded airline and airport operations, and, depending on the severity, they left thousands to millions of people stranded. Many of these were during peak travel seasons and lasted for days.

"I think it's a good thing it's sort of pre-Easter in a bit of a March lull moment," Ronan Murphy, a director at Alton Aviation Consultancy, told Business Insider. "If this is the middle of July, it would be an absolute disaster. You could have another 300 or 400 flights."

He estimates airlines could lose $80 to $100 million as they incur the expense of rerouting passengers and providing accommodations.

Many airlines are trying to curb the ripple effect and get planes heading to and from Heathrow as it re-opens.

United Airlines said it plans to operate most of its scheduled Friday flights to London. It also offered to reroute passengers through airports like Brussels or Amsterdam.

British Airways said it was cleared to operate eight long-haul flights to places like Johannesburg and Singapore on Friday. The flights will take off 16 and a half hours after Heathrow first closed.

The timing could have been worse, but it's still going to sting

According to the aviation analytics firm Cirium, some 1,300 flights were scheduled to take off or land at Heathrow on Friday, with a capacity of 290,930 seats. Heathrow is the world's fifth-busiest airport but ranks second for passengers flying internationally.

"If you think about load factor — let's say 75% full on average — that's 220,000 people, give or take, that are affected. That could be $100 million-plus of revenue for one day," Murphy told BI.

He said airlines wouldn't lose all of that because many passengers could be rerouted or choose to rebook for a later date.

He added that Heathrow is still "hugely profitable" and a vital airport for many carriers around the world.

"This is an unprecedented situation, and we have not seen a closure of Heathrow of this scale for many years," British Airways CEO Sean Doyle said. "Unfortunately, it will have a huge impact on all of our customers flying with us over the coming days."

With a capacity of 4 million seats last year, the New York-JFK to London Heathrow corridor is poised to be among the hardest hit as it is the 10th busiest route in the world — and the busiest outside Asia, according to data from OAG.

Flights from JFK to Heathrow from Thursday night to Friday morning were canceled or diverted, but FlightAware data shows most Friday night flights are not yet disrupted.

On Friday afternoon, around 14 hours after shutting down, Heathrow announced it was "safely able to restart flights, prioritizing repatriation and relocation of aircraft."

Getting planes to Heathrow is an important step in recovering operations — clearing the backlog so future scheduled flights can take off.

Travel expert Mike Arnot told BI the cost could be hundreds of millions of dollars, but large airlines typically have spare capacity and can take advantage of their alliance partners.

"I'm hopeful this incident will turn out to be a molehill, not a mountain," he said. "These are airlines that earn billions of revenue, where diversions, be it for weather during hurricane season or wintry mix, or mechanical issues cause irregular operations as part of doing business."

Major flight disruptions have cost airlines millions of dollars in the past

The 2010 eruption of Iceland's Eyjafjallajökull volcano released ash into the atmosphere, creating widespread chaos for air travel during the busy spring break travel period.

According to the International Air Transport Association, the eruption closed hundreds of airports across much of Europe's airspace for about a week, canceled about 100,000 flights, and impacted some 10 million people.

Airlines lost about $1.7 billion in revenue. The US-UK market was a major money-loser, accounting for $25 million of revenue a day.

A handful of more recent meltdowns — which snowballed due to misplaced planes and crew and broken infrastructure — have also halted travel and bled airline cash.

A January winter storm that swept through the southeast of the US affected operations at airports like Atlanta, New Orleans, and Houston. Thousands of flights and passengers were disrupted as airports shut down.

The same month, wildfires in Los Angeles also affected several airports across Southern California. At an investor conference hosted by JPMorgan in March, Delta Air Lines CEO Ed Bastian said January's disasters cost the carrier about $100 million.

Delta also lost $500 million after a botched CrowdStrike update caused a mass meltdown in July 2024 — during the peak summer travel season.

While other airlines affected by the outage recovered relatively quickly, Delta's problems lasted five days and led to nearly 5,500 flight cancellations.

Southwest Airlines experienced a meltdown in December 2022 when its outdated scheduling software lost track of pilots and flight attendants, causing nearly 17,000 flight cancellations. The ripple effect occurred during the holiday period.

The chaos cost Southwest over $1 billion, including a civil penalty payment to the Department of Transportation and reimbursements and refunds to passengers.