Campaigners against a third runway at Heathrow are facing a Government bid to block their legal challenge getting off the ground.
A coalition of local councils, including Hillingdon, Richmond, Wandsworth and Windsor and Maidenhead, together with Greenpeace UK and a Hillingdon resident, have brought a judicial review at London's High Court.
It claims that the Government's October 2016 decision to back plans for the runway frustrates the legitimate expectations of councils and residents who have received clear and repeated promises from ministers over the years that it would never be built.
It is also challenging the decision on the basis that the Government allegedly failed to recognise the project's unlawful air quality impacts.
Lawyers for the Secretary of State for Transport will ask Mr Justice Cranston to strike out the case today.
They say that a judicial review should not be heard until after the consultation on the National Policy Statement (NPS) on aviation is published in 2017/18.
Greenpeace UK executive director John Sauven said that the challenge was being brought because the Government had "not done their homework" on London's illegal levels of air pollution.
"There is no good reason to depart from the repeated Government promise that, because of the insuperable environmental problems, there should be no third runway.
"Since the ClientEarth case it's become even clearer that an expanded Heathrow is bound to make air pollution worse.
"The Government has not attempted to meet our case.
"Instead it is mounting a technical argument to strike it out, arguing that it cannot be brought until there is a formal decision, preceded by a consultation, to support Heathrow in a National Policy Statement.
"We want to challenge now because the consultation, without dealing first with air pollution, would be flawed at the outset and a huge waste of time, energy and public money.
"It will cause prolonged and unnecessary distress for thousands of residents.
"Until there is a solution to the pollution and noise caused by expanding an airport in a densely populated area, the Government should stick to its promise that a third runway is ruled out."
The hearing is expected to last two days.