Hundreds of thousands of passengers were left stranded on 21 March 2025 when a fire at an electricity substation in west London forced Heathrow Airport to shut for almost an entire day, triggering what analysts say is the UK’s single biggest flight disruption of 2025 so far.

With more than 1,300 flights cancelled or diverted and knock-on disruption lasting for days, attention has quickly turned to what, if anything, affected travellers can claim in refunds, rerouting and compensation of up to £520 under UK air passenger rights.

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How the Heathrow shutdown unfolded

The crisis began late on 20 March when a major fire broke out at the National Grid North Hyde substation in Hayes, a key node in the power supply that feeds Heathrow and tens of thousands of nearby homes. Flames and thick smoke were visible for hours as more than 70 firefighters battled the blaze and a 200 metre safety cordon was established around the site.

The fire led to a sudden and extensive power loss across Heathrow, cutting electricity to key systems in terminals, airfield operations and security. Backup arrangements proved insufficient to safely maintain operations at Europe’s busiest hub. Within hours, Heathrow announced that the airport would be closed to all flights until 23:59 on Friday 21 March, citing passenger and staff safety.

Flight data services reported that more than 1,300 arrivals and departures scheduled for that day alone were either cancelled or heavily disrupted, with up to 291,000 passengers potentially affected over the main closure period and subsequent recovery. Flights already en route to London were diverted to airports including Gatwick, Paris Charles de Gaulle, Shannon and other hubs, while some long-haul services turned back to their origin.

The scale of disruption across airlines and routes

Heathrow’s role as the UK’s primary long-haul gateway and a critical global transfer hub meant the impact rippled far beyond London. British Airways, which operates just over half of Heathrow’s traffic, was forced to cancel the bulk of its schedule for 21 March and significantly reduce operations over the following weekend as aircraft and crew were repositioned and congestion built up in terminals.

Other major carriers, including Virgin Atlantic, Lufthansa, Emirates, Qatar Airways and multiple US and European airlines, reported widespread cancellations and diversions. Brussels Airlines, for example, cancelled all its Heathrow services on the day of the closure, advising passengers not to travel to the airport and to rebook or seek refunds through their usual channels.

Analysts estimated that the shutdown was costing airlines tens of millions of pounds per day in lost revenue and operational disruption. Heathrow itself told lawmakers that the incident interrupted journeys for around 270,000 passengers and that implementing a full “seamless” power-resilience upgrade to prevent a repeat could carry a price tag of more than £1 billion.

Why most passengers will not get cash compensation for the closure

The central frustration for many travellers is that, despite the chaos, most of those affected by the Heathrow shutdown are unlikely to be entitled to cash compensation under UK air passenger regulations. The explanation lies in how the law treats so called “extraordinary circumstances”.

UK rules on flight delays and cancellations, carried over from EU Regulation 261/2004, set out fixed compensation amounts for passengers whose flights arrive three hours or more late, or are cancelled at short notice, when the airline is responsible for the disruption. However, when delays and cancellations are caused by events that are genuinely outside the airline’s control, carriers are not obliged to pay that compensation, even when the impact on passengers is severe.

An external power cut caused by a fire at a third party electricity substation fits squarely into the “extraordinary circumstances” category, similar to severe weather, air traffic control failures, volcanic ash clouds or security incidents. Industry bodies and travel rights experts have been clear that the Heathrow incident is expected to be treated as such, meaning airlines will argue they are exempt from mandatory cash payouts related directly to the shutdown itself.

What you are still entitled to when a flight is cancelled

Even when an airline is not at fault, it does not mean passengers are left without protection. Under UK law, carriers must still offer travellers on cancelled flights a choice between a full refund and an alternative journey at the earliest opportunity, whether on their own services or, in many cases, on those of rival airlines.

If your flight to or from Heathrow was cancelled because of the closure, you are entitled to a refund of your unused ticket if you choose not to travel, or to be rebooked onto the next available service to your destination. This applies whether the ticket was one way or part of a return trip, and whether or not the airline ultimately pays compensation.

In addition, airlines have what is known as a “duty of care” to customers who are stranded by disruption, regardless of the cause. That includes providing food and drink after a certain waiting time, access to communication such as phone calls or emails, and hotel accommodation and transport between the airport and hotel when an overnight stay is required. If an airline cannot arrange this directly, passengers may purchase reasonable meals and lodging themselves and later claim back the costs, supported by receipts.

When the £220 to £520 compensation rules apply

The widely quoted figures of up to £520 in flight delay compensation remain highly relevant in general, just not usually in the context of the Heathrow substation fire. These amounts are based on flight distance and length of delay on arrival under the UK’s interpretation of the EU-style rules.

For flights departing from or arriving in the UK on a UK or EU airline, passengers can normally claim around £220 for short-haul flights (up to 1,500 kilometres), higher amounts for medium-haul routes, and up to £520 for long-haul journeys of more than 3,500 kilometres when arrival is delayed by at least four hours or when a flight is cancelled at short notice and the airline is responsible. Where the delay is slightly shorter, the long-haul amount can drop to £260.

To qualify, three main conditions must be met. First, the flight must be within the scope of UK or EU passenger rights, which usually means departing from a UK or EU airport or operated by a UK or EU carrier. Second, the delay or cancellation must be within the airline’s control, such as a technical fault with the aircraft, crew shortages, poor scheduling or other operational failures. Third, the delay at arrival must reach the minimum thresholds and, for cancellations, the airline must have given less than 14 days’ notice.

How Heathrow’s chaos could still trigger compensation in some cases

While the substation fire itself is expected to count as an extraordinary circumstance, there are scenarios around the Heathrow shutdown where compensation may still be payable. The key is whether the proximate cause of an individual delay or cancellation was the external incident, or separate problems for which the airline can be held responsible.

If, for instance, you were booked on a flight several days after the airport formally reopened and your service was cancelled or significantly delayed because the airline had mismanaged crew schedules or aircraft positioning during the recovery, you may have grounds to argue that your particular disruption was no longer directly linked to the power outage. In that case, standard compensation rules could apply, including potential payouts of up to £520 on long-haul routes.

Similarly, if your flight was rerouted away from Heathrow but then heavily delayed or cancelled due to an airline specific issue at the alternative airport, you could be covered. Claim assessors will look at timelines, airline communications and operational records to determine whether the extraordinary circumstances defence genuinely applies to your situation or whether it has become a convenient umbrella to deny otherwise valid claims.

How to check if you can claim up to £520

Travellers affected by the Heathrow shutdown should begin by gathering their documentation. Keep boarding passes, booking confirmations, email and text alerts from the airline, and any receipts for expenses such as meals, hotels and ground transport. Note the exact scheduled and actual departure and arrival times for your flight, as well as any alternative arrangements offered.

Next, check whether your journey falls within the UK or EU compensation framework. If your disrupted flight departed from a UK airport, it is covered regardless of airline. If it departed from elsewhere but was operated by a UK or EU carrier and was due to land in the UK, the rules also apply. Long haul flights of more than 3,500 kilometres are eligible for up to £520 in compensation when the airline is responsible and the delay on arrival reaches at least four hours, although in some cases this maximum can be reduced to £260.

You should then assess the likely cause of your disruption. If your flight on or around 21 March was cancelled purely because Heathrow was closed, you are almost certainly limited to a refund or rerouting and duty of care, without additional compensation. If your delay occurred days later or involved further complications seemingly unrelated to the power cut, you can submit a formal claim to the airline citing the applicable compensation levels and explaining why you believe extraordinary circumstances no longer apply in your case.

Practical steps for refunds, rerouting and expenses

In the immediate aftermath of a major disruption such as the Heathrow fire, airlines typically prioritise getting passengers moving again before handling financial claims in full. The fastest way to secure your options is usually via the airline’s app or website, where self service tools increasingly allow you to request a refund, choose alternative flights or accept vouchers.

If online rebooking is not available or the choices offered do not meet your needs, contact the airline’s customer service by phone or, if advised it is safe to do so, approach their airport desk at your current location rather than at Heathrow itself. Under UK rules, if the airline’s next available flight is not reasonably soon and there is space on a rival carrier, you can ask to be reprotected on that competitor, especially on longer routes where delays could extend into days.

For duty of care expenses, keep receipts for everything from water and snacks to hotel stays and ground transfers. When you later submit these to the airline, ensure they are reasonable in the context of your delay and location. A basic mid range hotel close to the airport is more likely to be reimbursed in full than a luxury downtown suite, unless the airline expressly arranged it.

Role of travel insurance and future rule changes

Because extraordinary circumstances shut off the main route to statutory compensation, travel insurance often becomes the crucial safety net in situations like the Heathrow shutdown. Many comprehensive policies include benefits for travel delay, missed connections and additional accommodation and transport costs arising from external events such as power failures, infrastructure incidents and security scares.

Policyholders should review their cover limits and exclusions, then submit claims promptly with the same supporting documents they provide to airlines. Some insurers also offer lump sum payouts after a specified number of hours of delay, regardless of who was at fault, which can soften the financial blow when statutory compensation is unavailable.

Meanwhile, wider changes to European air passenger rights are on the horizon. EU transport ministers have agreed in principle to revise compensation rules, increasing delay thresholds and altering payout levels, especially for long haul flights. Although the UK now runs its own regime, those reforms may still affect British travellers on EU carriers and could influence future adjustments to the UK system, including how events like the Heathrow power failure are treated in law.

For now, passengers caught up in the UK’s biggest flight disruption of 2025 face a patchwork of rights: strong protections on refunds, rerouting and care, but sharply limited access to the headline compensation sums of up to £520 unless they can show their specific delay or cancellation stemmed from failings under the direct control of their airline rather than from a fire in a substation several kilometres away.