Heathrow clings to Europe’s busiest airport title by just 40,000 passengers – Istanbul closing in fast
Heathrow held on to its spot as Europe’s busiest airport in 2025, handling 84.48 million passengers – a modest rise of 0.7% from the year before.
But the margin is razor-thin. Istanbul clocked 84.44 million passengers, up a sharp 5.5%., a difference of only 40,000 travellers, and close enough that many in the industry expect the Turkish hub to overtake Britain’s flagship airport sometime in 2026.
The figures come from ACI Europe’s latest traffic report published on Thursday (5 February). Europe as a whole smashed records with 2.6 billion passengers across the network – up 4.4% on 2024, adding 100 million more flyers despite high fares, sluggish economies, and geopolitical tensions.
International travel drove the growth (+5.6%), while domestic stayed flat (+0.2%). Airports outside the EU+ bloc outperformed (+6.2%) compared to EU+ hubs (+4%), thanks to less mature markets and higher growth potential.
Why Heathrow’s growth lagged
Heathrow’s small increase came from airlines packing more seats into larger aircraft at the already maxed-out site, with no new capacity added.
UK airports overall grew just 1.7% in 2025, well below the European average. ACI pointed to “punitive taxation regimes” as a key drag, especially on domestic routes. France and Germany saw even steeper domestic drops versus pre-pandemic levels (-27% and -48% respectively).
Eastern Europe stole the show: Slovakia (+20.2%), Poland (+14.4%), Hungary (+11.1%), and others posted double-digit gains. Low-cost carriers expanded aggressively there, while UK and Western hubs felt the pinch from taxes and policy headwinds.
Over the past five years, Istanbul’s passenger numbers have jumped nearly 25%. The hub benefits from strong low-cost carrier growth, geographic position, and fewer capacity limits than Heathrow.If trends continue, 2026 could see the switch. Heathrow’s constraints – slot limits, no new runway progress – make catching up tough without policy changes.
Heathrow’s third runway
In June 2025, the government published the UK’s 10-year infrastructure strategy, which included an explicit invitation for proposals to build a third runway as part of a £725 billion effort to tackle chronic underinvestment and support economic growth.
Chancellor Rachel Reeves endorsed the broader strategy of improving connectivity, reducing travel costs and delays, and meeting environmental and climate targets – although no dedicated funding or precise timeline was assigned to the runway, with £24 billion allocated to transport maintenance and projects such as East West Rail.
A July 2025 Labour Together think tank paper examined options to accelerate the third runway to delivery by 2029 – ahead of the next general election – through a bespoke public bill and special development order. This could reduce approval timescales to seven months, avoiding the standard six-year development consent order process and related judicial reviews, with decisions transferred to ministers.
The paper presented the project as a “tangible achievement” for the government, highlighting potential for lower holiday costs, improved job access and greater economic confidence in a challenging global context. A short-haul-focused runway could limit M25 disruption while freeing the main runways for additional long-haul services.
Against the backdrop of today’s new air traffic report, these proposals carry added weight. With Istanbul up 5.5% and now only 40,000 passengers behind, poised for an overtake in 2026, a third runway providing new slots by 2029 could help counteract the UK’s sluggish 1.7% growth, which ACI links to taxation and infrastructure bottlenecks.
It might enable Heathrow to defend its position for longer – provided momentum builds quickly. Environmental mitigation measures, public consultations and regulatory challenges remain significant barriers. Without decisive progress, Istanbul’s momentum is likely to prevail.
