More than 40 airlines are seeking slots at London Heathrow, the airport said on October 12, 2026, as demand for access continues to exceed the capacity Europe's busiest hub can legally allocate.

Heathrow's management said the shortfall forces carriers to "choose competing hubs overseas", a dynamic it argues is "taking connectivity, trade and growth opportunities away from the UK". The claim lands at a politically sensitive moment: in a September 2026 interview, the UK Prime Minister appeared to refuse to back a third runway, and London Mayor Sadiq Khan remains a long-term opponent of further expansion.

What does the capacity constraint mean for airlines and fares?

Heathrow argues a larger airport would create room for new airlines and new routes, increase competition and drive down fares for consumers. The airport's own traffic figures frame the stakes.

• Almost 7.2 million passengers used Heathrow in September 2026, down 2.3% year-on-year.
• Travel to the Middle East fell 20% during the month, while Asia-Pacific traffic grew.
• Almost 1.4 million of September's passengers were transfers.
• Cargo volumes rose 5% year-on-year.
• More than 84 million passengers passed through in the last 12 months.

The airport says the transfer traffic is what makes additional destinations commercially viable for UK passengers and businesses, and describes itself as "the UK's largest port by value" on the strength of its cargo throughput.

Who is backing expansion — and who is not?

Heathrow claims a growing coalition of politicians, trade unions, businesses, workers, regional airports and airlines supports a third runway, and says polling shows 68% of local people favor progressing the project.

"Airlines as well as airports across the UK, including Aberdeen, Belfast City, Cornwall Newquay, Glasgow, Leeds, Newcastle and Teesside all want Heathrow to expand at pace to improve connectivity and enable growth," a Heathrow spokesperson said.

That regional-airport endorsement matters politically, because opponents of expansion have long argued a bigger Heathrow would drain traffic from the rest of the UK. The counterweight remains the Prime Minister's apparent reluctance and Mayor Khan's sustained opposition.

What happens at the Transport Select Committee?

Later this week, Heathrow CEO Thomas Woldbye will give evidence to the Transport Select Committee's hearing on the Heathrow Expansion National Policy Statement (HENPS), the document that parliament is currently reviewing and that would set the planning framework for a third runway.

"This is not simply an investment in an airport. It is an investment in the UK's future competitiveness," Woldbye said. "At a time when other international hubs continue to grow and attract new routes, this country has an opportunity to strengthen its global connections and unlock growth in every nation and region."

Woldbye also asserted the financing and environmental case is closed. "There is now a clear path forward," he said. "The private investment is available, the benefits are well understood, and the Government has confirmed expansion can be delivered within net zero targets. After decades of discussion, Parliament now has the opportunity to unlock a project that can deliver lasting benefits for generations to come. We are ready to deliver it."

The airport's claims warrant scrutiny against delivery reality. No third runway has been built in the decades the project has been debated, and the HENPS review gives parliament — not the airport — the decisive voice. Still, the 40-airline queue is a hard indicator of constrained supply: Heathrow's two runways operate near their movement limits, and each new entrant requires another carrier to give up capacity. Woldbye's appearance before the committee will test whether the political arithmetic on expansion has shifted before parliament settles the policy statement.