PLANS for the construction of Heathrow's third runway have been approved by the Prime Minister.

The economic sub-committee, of which Theresa May is the chairwoman, has signed off the plans for Heathrow's third runway, which have also been backed by full cabinet. The plans will now be debated on in Parliament in the coming weeks.

The transport secretary, Chris Grayling, said the plans symbolised "the government's commitment to securing global connectivity, creating tens of thousands of local jobs and apprenticeships, and boosting our economy for future generations, by expanding Heathrow airport.

"My department has met with local residents, and fully understand their strength of feeling. But this is a decision taken in the national interest."

Despite fierce opposition from some MP's and local authorities, the third runway is highly likely to be approved. The third runway is supported by incumbent Conservative party, and Labour also conditionally supports the runway, if Heathrow can prove it can meet certain standards of noise and air quality.

The question remains, however, if Mrs May will use the whip to silence critics within her own party, which include MP for Windsor, Adam Afriyie, and foreign secretary Boris Johnson, in order to get the plans pushed through by the end of the month.

Meanwhile, the Royal Borough of Windsor and Maidenhead intend to launch a legal challenge over the third runway if it does not meet their standards. Council leader Simon Dudley said: "We will now be reviewing the National Policy Statement (NPS) to see if our significant concerns have been addressed. We will be liaising with our partner authorities, who represent over one million residents, to see if they have addressed our concerns. Any legal challenge will need to be launched within six weeks, so we're on a tight timetable."

Slough Borough Council, which has been a long-time supporter of Heathrow, expressed delight with the move. Leader of the council, James Swindlehurst, said: "The economic opportunities expanding Heathrow will bring to our town and residents will significantly improve Slough - from jobs and regeneration to local transport infrastructure and facilities.

"Expanding Heathrow is the right decision for Slough as a place and the country as a whole."

If the third runway is ultimately approved, Heathrow will send out more detailed plans for public consultation in 2019, and then to a planning inquiry in 2020.

The plans, possibly altered as a result of the public consultation and the inquiry, would then likely be approved by the Transport Secretary in 2021, allowing construction to commence. Heathrow currently anticipates that the runway will be open around 2025.