Thomas Woldbye, chief executive of Heathrow Airport, warned that not building a third runway would represent a "huge missed opportunity" for the UK, telling BBC Radio 4's Today programme that private investment capital would flow elsewhere if the project does not proceed.
Woldbye said investors, a consortium including French private equity firm Ardian, Qatar Investment Authority, Saudi Arabia's Public Investment Fund and China Investment Corporation, would deploy their funds internationally rather than in the UK if expansion cannot move forward. He suggested a decision would be made in the new year.
Prime Minister Andy Burnham has declined to state whether the government backs the expansion. As Mayor of Greater Manchester, Burnham opposed the scheme. He told the BBC the matter was "for London and Londoners" and said he wanted to hear from local people first before taking a position.
The Department for Transport said it is reviewing consultation responses and considering "appropriate next steps". A spokesperson stated the government supports airport expansion "across the country where this can contribute to growth and opportunity, while meeting the tests on the environment", and cited potential £40 billion in economic benefits.
A third runway has been debated for decades and faces opposition from residents, politicians and climate campaigners. The project would require demolishing hundreds of homes, diverting rivers and rerouting the M25 motorway through a tunnel beneath the new runway. Construction costs are estimated at £33 billion.
Heathrow currently serves over 80 million passengers annually with flights capped at 480,000 per year. A third runway would raise that cap to 720,000 flights annually, or nearly 2,000 per day on average.
The Department for Transport is finalising its Airports National Policy Statement, last updated in 2018, which provides the basis for deciding whether to grant approval. Woldbye said Heathrow plans to submit a planning application within the next couple of years.
When questioned about noise impacts on nearby communities, Woldbye claimed Heathrow has seen a "stark" reduction in noise over the past 40 years and the trend would continue. He added that "years of uncertainty" represented his biggest concern and called for the government to provide clarity on the project.