Andy Burnham has refused to back the expansion of Heathrow Airport, withholding his support for one of the most contested infrastructure projects in UK aviation.

The mayor's position, reported by Building, places him among the senior political figures who decline to endorse the growth of Europe's busiest hub. Burnham, who leads Greater Manchester, has long positioned himself as a voice for the north of England in debates dominated by London-centric infrastructure spending.

His refusal to back Heathrow expansion comes as the project continues to divide opinion across Westminster and the regions. Supporters of a third runway argue that additional capacity at Heathrow is essential for the UK's long-haul connectivity and its ability to compete with rival European hubs. Opponents point to the environmental cost, the noise burden on communities under flight paths, and the concentration of aviation investment in the southeast.

For the airline industry, the political arithmetic matters. Heathrow has operated at capacity for years, with its two runways handling more traffic than any other airport in Europe. Carriers seeking additional slots — particularly for long-haul services to growth markets in Asia and the Americas — have long argued that constrained capacity pushes transfer traffic and the economic activity it generates to competitors such as Paris Charles de Gaulle, Amsterdam Schiphol and Frankfurt.

Burnham's stance also reflects the regional dimension of the debate. Politicians in the north of England have repeatedly argued that aviation policy should spread growth beyond the southeast, pointing to underused capacity at airports such as Manchester itself, as well as Birmingham and Liverpool. Any decision that concentrates additional runway capacity at Heathrow raises questions about how the government balances investment between London and the regions.

The refusal adds political friction to a project that has already spent more than a decade working its way through planning, parliamentary votes, judicial review and repeated policy reversals. Heathrow's operators have continued to press the case for expansion, but political endorsements remain uneven, and each senior figure who declines to back the scheme complicates the path to a final investment decision.

Environmental considerations weigh heavily in the current debate. Campaigners oppose expansion on climate grounds, arguing that a third runway is incompatible with the UK's legally binding net-zero commitments. That argument has gained force with successive court rulings and shifting government positions on aviation emissions.

Burnham has not framed his position as outright opposition in the reported remarks, but his refusal to offer support signals that Heathrow's expansion cannot yet count on a cross-party, cross-regional consensus. How the government responds — and whether it can assemble the political coalition needed to deliver new runway capacity in the southeast — will shape the trajectory of UK airport policy for years to come.