Istanbul airport overtook Heathrow as Europe’s busiest airport in July, handling 8.15 million passengers against the west London hub’s 7.86 million, prompting Heathrow to say its “case for expansion has never been clearer”.

Figures published on Tuesday showed Heathrow’s July passenger total was 1.5 per cent lower than the same month last year, while Istanbul recorded a 2.3 per cent increase.

For more than two decades before the pandemic, Heathrow served more passengers than any other European airport, according to annual figures from the trade body Airports Council International. The UK’s biggest airport lost that position in 2020 amid coronavirus travel restrictions before regaining it in 2023.

Heathrow’s two runways operate at near full capacity and the airport is seeking government permission to build a third. Its £33bn expansion plan would enable it to accommodate 150 million passengers a year.

In a statement, the airport said: “The case for expansion has never been clearer, as Heathrow was overtaken in July by Istanbul airport as the busiest hub in Europe.

“Our plans will ensure the country gets the infrastructure it needs to stay competitive and will deliver all-important economic growth.”

The two hubs operate under different conditions. The current Istanbul airport opened in late 2018 on a new site away from the city and residential neighbourhoods, gradually replacing Ataturk airport as Turkey’s main international hub. It has a far larger footprint than Heathrow and is able to operate 24 hours a day.

Selahattin Bilgen, Istanbul airport’s chief executive, said the news was “a significant milestone for our airport”.

“Thanks to our three independent runways, which can be operated simultaneously 24 hours a day, our advanced operational capabilities and high capacity, we have successfully overcome the capacity constraints faced by many major global hub airports,” he said.

“With the addition of our fourth runway, which is set to become operational by the end of this year, we aim to take this growth even further by increasing the capacity we provide to airlines and passengers while elevating the quality of our services to the next level.”

The transport secretary, Heidi Alexander, launched a consultation on the Heathrow expansion national policy statement in June, setting out the conditions for the third runway to go ahead. The then chancellor, Rachel Reeves, said at the time that she was determined to get “spades in the ground” in the current parliament, and for the runway to be built by 2035.

The plans face opposition. Andy Burnham, the mayor of Greater Manchester, has previously said Heathrow expansion diverts infrastructure investment “away from the north and traps it in London”. Airlines including IAG and Virgin Atlantic have called on the Civil Aviation Authority to review Heathrow’s charging framework before a third runway is approved, warning that the costs would be passed on to passengers.

Thomas Woldbye, Heathrow’s chief executive, said: “Expanding Heathrow will help ensure the UK remains home to Europe’s leading hub and continues to benefit from the trade, investment and tourism that increased connectivity will bring.”

Elsewhere, July was a record month at two other UK airports. London Stansted said it recorded its busiest month ever, welcoming 3.1 million passengers, a 6.3 per cent increase year on year. Manchester also had a record July, serving 3.4 million passengers.