The SNP is expected to back the UK Government’s decision to go ahead with a new Heathrow runway in a crucial Commons vote despite Tory backbench opposition.
Prime Minister Theresa May has permitted ministers with long-standing opposition to the scheme to voice their views at a local level.
Arch critic Foreign Secretary Boris Johnston is tipped to miss the vote by being abroad.
Transport Secretary Chris Grayling yesterday announced plans to press ahead with a third runway at the UK’s sole hub airport three years after it was recommended by a government-appointed commission into expanding Heathrow or rival Gatwick.
Ministers are expected to have to rely on opposition parties such as the SNP to get the plans approved next month.
The SNP refused to comment officially but a source said it was “broadly in favour of Heathrow expansion due to the economic benefit it would bring to Scotland”.
It added: “A decision on the vote will be taken when details become available.”
Backing would see rare agreement between the UK and Scottish governments, with Scottish Secretary David Mundell describing Mr Grayling’s announcement as “a step forward for Scotland”.
The Scottish Government is counting on more Scottish flights, boosting tourism and business links.
Economy secretary Keith Brown said: “We will now push for clarification from the UK Government about a number of issues, including how it intends to guarantee [landing] slots for Scotland.
“Building a third runway at Heathrow has the potential to provide the most significant benefits to the country’s economy and connectivity.”
Mr Brown also referred to Heathrow’s pledge to base a “logistics hub” in Scotland for the project, perhaps at Prestwick Airport, as an important part of its offer.
Business groups reaffirmed their backing for Heathrow.Scottish Chambers of Commerce chief executive Liz Cameron said they looked to MPs to “green light this vital infrastructure project”.
However, Edinburgh Airport, which is co-owned with Gatwick, said: “We remain unconvinced of the argument for Heathrow and its ability to successfully build a third runway. We are sceptical about this happening at all.”
The Scottish Liberal Democrats condemned the plans as “expensive folly that will badly hurt the environment”.
The Scottish Greens said growing aviation “makes no sense”.