Istanbul airport has overtaken Heathrow as Europe’s busiest airport by passenger numbers, leading the London hub to say its “case for expansion has never been clearer”.

Figures published on Tuesday showed 7.9 million passengers passed through Heathrow’s terminals in July, compared with Istanbul’s 8.15 million.

Heathrow’s passenger numbers for July fell, while London Stansted and Manchester both had record traffic for the month.

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, located in west London, lost its pre-eminent position in 2020 amid coronavirus travel restrictions before regaining it in 2023.

Heathrow’s July passenger total was 1.5% down compared with the same month last year, partly due to the war on Iran, while the Turkish hub recorded a 2.3% increase.

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

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 comparison, however, may not fully bolster Heathrow’s case. The current main Istanbul airport was only opened in late 2018 and built on a brand new site away from the city and residential neighbourhoods, gradually replacing the existing Ataturk airport as the main international hub. It has a vastly bigger footprint and is able to operate 24 hours a day.

The Turkish boom also owes much to its location near the Gulf, which has become the crossroads of international air travel.

Istanbul airport’s chief executive, Selahattin Bilgen, 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 renamed 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 it to be built by 2035.

Andy Burnham, however, has previously expressed concerns over Heathrow expansion, saying the plans divert infrastructure investment “away from the north and traps it in London”.

Heathrow’s chief executive, Thomas Woldbye, 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.”

London Stansted said it had recorded the busiest month ever in July, welcoming 3.1m passengers, a 6.3% increase year-on-year.

Manchester also had a record July, serving 3.4m passengers.