Three weeks after Heathrow closed down for almost a day due to a power substation fire, Britain’s biggest airport has reported a 7.5 per cent fall in passenger numbers – but the hub still expects to handle a record number of travellers in 2025.

During March, Heathrow handled 6.22 million passengers – almost half a million fewer than in the corresponding month in 2024.

The number of flight movements dropped by 3 per cent, which represents about one full day of flying.

A fire broke out in a transformer within the North Hyde electrical substation in Hayes, north of Heathrow, late in the evening of Thursday 20 March.

The airport later said: “The decision to close the airport was taken to protect passenger and colleague safety because of the unprecedented impacts of an off-airport fire at an electrical substation.”

Read more: Heathrow Airport shutdown – what we learnt from travel chaos and how could it be prevented?

More than 1,300 flights were diverted or cancelled by the near-total shutdown of Heathrow on Friday 21 March. A few flights were allowed to arrive and depart later in the day. A further 100 or more were grounded on the following day as airlines struggled to get their operations back on track.

More than 250,000 passengers had their travel plans wrecked.

In his commentary on the fall in traffic, the chief executive, Thomas Woldbye, did not refer to the fire, saying: “Passenger numbers were slightly down due to changing holidays this year.”

Easter fell in March in 2024, increasing the amount of traffic in that month. This year Easter falls in late April. Ramadan – which normally causes a reduction in passenger numbers – coincided with March this year. Traffic to and from the Middle East was down 8 per cent year-on-year.

The decline in Heathrow’s traffic in March led to an overall fall of 1.5 per cent in the first quarter of 2025.

Mr Woldbye added: “Belly hold cargo on passenger flights was a bright spot, growing 4 per cent, and underlining the importance of Heathrow as the UK’s gateway to growth.

“We are still on track to see another record year in 2025 and colleagues are working hard preparing for a busy Easter and May Bank Holiday getaway.”

Two inquiries are under way into the closure of Heathrow. At a hearing of the Transport Select Committee earlier this month, Mr Woldbye said the bill for setting up a guaranteed power supply would be more than £1bn.

Airlines lost up to £100m as a result of the airport’s closure. But away from Heathrow, the shutdown boosted the fortunes of other airports and airlines. Ryanair sold an extra 10,000 tickets on the day, many of them to and from London Stansted.