Last year, Heathrow Airport experienced a shutdown that led to the most significant flight disruption in the UK for 2025. This unexpected event unfolded on March 21 after a sudden power outage forced the airport to cease operations temporarily.

The root of the problem was traced to a major electrical substation owned by National Grid that exploded and caught fire in Hayes, a west London suburb located less than two miles from Heathrow. This unexpected incident created a ripple effect of chaos, though the airport was able to resume its full schedule the following day.

On that fateful day, approximately 220,000 travelers were scheduled to pass through Heathrow. The outage resulted in over 1,000 flights being delayed, canceled, or rerouted, impacting nearly every passenger using the airport.

Recent findings from AirHelp, an organization dedicated to air passenger rights, revealed the vast extent of this disruption, underscoring the profound effect it had on air travel operations through one of the world’s busiest airports.

However, around 220,000 people were due to travel through Heathrow on March 21 and more than 1,000 flights were delayed, cancelled or diverted. 

New data from AirHelp, an air passenger rights organisation, found that almost all passengers travelling via the airport were affected.

Some 99 per cent of travellers experienced disruption to their journeys and 98 per cent of all flights were cancelled completely. 

The shutdown as been named the most severe single disruption for UK aviation in 2025.

The Daily Mail approached Heathrow Airport for comment. 

The major hub was shut down on March 21, 2025 after being hit by an unexpected power outage

The year worked out to be chaotic for air travel overall, with 940,000 flights and 36 million passengers hit with delays or cancellations. This works out as 26 per cent of all air travellers facing issues during their journeys last year.

Delayed passengers could be entitled to free meals and compensation of up to £520 if their flight was disrupted as part of the Heathrow closure.

Airline passengers delayed by two hours or more could be entitled to assistance such as two free phone calls or emails, free meals and refreshments, free hotel accommodation and hotel transfers, according to Which?, outlining the following:

Short-haul – Passengers flying up to 932 miles (1,500km) with a delay time of at least two hours are entitled to assistance.

Medium-haul – Passengers flying between 932 miles (1,500km) and 2,175 miles (3,500km) with a delay time of at least three hours are entitled to assistance.

Long-haul – Passengers flying more than 2,175 miles (3,500km) with a delay time of at least four hours are entitled to assistance.

Delayed passengers who meet the above criteria can contact their airline or approach staff at the airport for further information.

For severe delays of more than five hours, passengers are ‘entitled to choose between being rerouted on a different flight or getting a refund’, Which? says.

Around 220,000 people were due to travel through Heathrow that day and more than 1,000 flights were delayed, cancelled or diverted

Travellers can also request flight delay compensation, according to the watchdog, ‘if the delay is not due to extraordinary circumstances’. These include bad weather, strikes unrelated to the airline, such as with baggage handlers, acts of terrorism or sabotage, drone disruption and long security queues.

Claims are valid for up to six years after the flight was due to fly in or out of the UK, it adds.

As for how to claim, you need to contact the airline you were due to fly with.

‘If your flight arrives at its destination more than three hours late, each affected passenger is entitled to claim flight delay compensation,’ Which? says.

The total value of compensation depends on the length and distance of the delayed flight as well as the reason for the delay, it adds.

Passengers travelling less than 932 miles (1,500km) whose new flight takes off more than one hour before their original flight and arrives less than two hours after it are entitled to £110 in compensation, according to Which?.

If the passengers’ flight arrives more than two hours after the original flight, they are entitled to £220 in compensation, it adds.

Passengers travelling 932 miles (1,500km) to 2,175 miles (3,500km) whose new flight departs more than one hour before their original flight and arrives less than three hours after it are entitled to £175 in compensation.

However, delayed passengers could be entitled to free meals and compensation of up to £520 if their flight is disrupted. 

If the passengers’ flight arrives more than three hours after their original flight, they are entitled to £350 in compensation.

Passengers travelling more than 2,175 miles (3,500km) whose new flight departs more than one hour before their original flight and arrives less than four hours after it are entitled to £260 in compensation.

If the passengers’ flight arrives more than four hours after their original flight, they are entitled to £520 in compensation.

The figures above are for flights cancelled less than seven days before departure.

‘If a connecting flight during your journey is affected by a delay and you departed from the UK or an EU country, you can still claim compensation,’ Which? adds.

‘For example, if you were flying from Manchester to Sydney, connecting in Singapore, but your Singapore to Sydney flight was delayed, you’d still be entitled.’

Tomasz Pawliszyn, AirHelp CEO, commented: ‘2025 was a challenging year for UK air travel, with millions of passengers experiencing delays or cancellations. 

‘The Heathrow closure in March was an extreme example, but our research shows disruption was widespread, from major airports to smaller regional hubs.

At least 1,351 flights to and from Heathrow will be impacted by the major closure

‘Many passengers affected may not realise they are entitled to compensation and understanding your rights is more important than ever.

‘Our report is designed to help travellers navigate these situations and ensure they can claim what they are owed.’

Elsewhere, Manchester was named the worst major UK airport for delays by air passenger rights experts at AirAdvisor after analysing data from the Civil Aviation Authority which covered the first six months of the year.

Manchester Airport, the third-busiest airport in the UK in terms of passengers, saw just 71.5 per cent of flights left on time.

This compares to the national average, where 77 per cent of flights from all UK airports were on time.