The airport’s bid for extra capacity as opposed to as Gatwick was lent a boost when the Scottish government agreed to sign a Memorandum of Understanding with the airport backing the move.
The Scottish government said the runway would offer significant strategic and economic benefits for the country, including the creation of 16,000 new jobs.
In addition, about £200 million would be spent on construction in Scotland while £10 million would be available for new domestic routes.
Prestwick airport would also be investigated as a potential site for a logistics hub to support the building of a third runway.
The Scottish government’s cabinet secretary for economy, jobs and fair work Keith Brown said: "In the absence of action from the UK government, we have made this decision and we would urge them to act as quickly as possible.
"We have been clear from the start of this process that we wanted the best deal for Scotland and building a third runway at Heathrow provides the most significant benefits to the country’s economy and connectivity.
"We have engaged extensively with both airports during this process and considered all options very carefully. Gatwick’s proposals are also to be commended.
"However, Heathrow’s plan offers significant job creation, major investment opportunities and, crucially, seeks to address how all of Scotland’s airports benefit from the new runway capacity when it comes and also in the lead-up period.
"The potential for a logistics hub to be based at Glasgow Prestwick Airport is also an important part of the Heathrow offer. It would support the pre-fabrication of components for the construction phase, with potential for future work beyond the launch of the third runway, bringing strong economic benefits to the airport and the wider Ayrshire economy."
Meanwhile, one of the most forthright critics of Heathrow expansion MP and foreign secretary Boris Johnson has backed down in his opposition to the scheme.
Having previously said he would lie down “in front of those bulldozers and stopped the building, The Times reported he has now indicated to prime minister Theresa May that he will not quit if the scheme gets the go ahead.
May used her keynote address at last week’s Conservative conference to promise the government would “shortly announce” a decision on airport expansion.
