MPs voted 415 to 119 to grant permission for a third runway on Monday, meaning the government has now formally adopted the proposals into the National Planning Statement. It gives opponents six weeks to now lodge objections in the courts.

The Department for Transport said approval “could see building work start in 2021”, but several groups are preparing challenges, among them the London Assembly, which pledged to seek to overturn “this calamitous decision”.

Greenpeace said it would join councils in a legal challenge. The environmental charity was part of a consortium that bought an acre of land near Heathrow in 2009 and divided it into small lots, allocating each to a different owner in a bid to scupper expansion. However, a Greenpeace spokesperson admitted this was not part of its latest strategy: “The current development plans are in a different place,” they said.

The court challenges, which will centre on the idea of expansion as a whole, are expected to begin in the autumn and will be based on the increased noise and air pollution a third runway will bring. If these are overcome, Heathrow will meet another hurdle after it submits detailed proposals next year, as this will face a planning inquiry that will not start until 2020.

Protest group Hacan (Heathrow Association for the Control of Aircraft Noise) admitted the MP majority voting in favour had been “a little higher than expected” and this gave the government “a strong mandate to build the runway”.

The project, costed at £14 billion, could increase capacity from 78 million to 130 million passengers a year, but will not be ready until 2026 at the earliest. A sixth terminal has also been suggested, although existing buildings may be extended instead.

Heathrow may also face objections from airlines, which have said they will oppose any increases in passenger charges to fund construction. Tim Alderslade, chief executive of Airlines UK, said: “We expect the secretary of state to enforce his stated aim of keeping passenger charges at today’s levels, but until we receive complete clarity on this our support for the new runway will remain conditional.”

Despite Heathrow mainly benefiting the south-east, the UK regions are largely supportive because a third runway may mean reinstatement and expansion of regional connections.

Heathrow no longer has flights from airports such as Newquay; while new links with cities such as Cardiff, which rely on connections through Dublin, Amsterdam and Paris, could be a possibility.