A final decision on whether to expand Heathrow or Gatwick will not be taken for another year, it has emerged.
Prime Minister Theresa May has told Cabinet colleagues in a letter that a ruling would be made in the winter of 2017-18.
A Cabinet sub-committee will reveal its preferred option next week and a "full and fair" public consultation will follow.
Expanding Heathrow has been strongly opposed by some cabinet ministers. After next week's meeting, ministers will be allowed to make their own views known in a break with convention. However, they will have to ask the prime minister's permission, and will not be allowed to criticise the government in the Commons nor to "actively campaign" against the government. Number 10 would not comment as to whether or not MPs would be able to vote freely on the matter. Allowing ministers to speak out could avert the possibility of resignations from Cabinet.
Earlier, Theresa May told ministers at Tuesday's Cabinet meeting that a decision on increasing airport capacity in the South East had been "delayed for too long" and that it was important to now take a decision "in the national interest", her spokeswoman said.
The nine members of the airports sub-committee do not include Foreign Secretary Boris Johnson, whose Uxbridge and South Ruislip seat is close to Heathrow, Putney MP Justine Greening or any other minister representing a London constituency. Mrs May's spokeswoman said the decision to give ministers a limited period to voice their personal views was a "mature, common-sense approach reflecting the fact that many ministers have long-held views and that ministers are also MPs and some have specific constituency issues that they have to address".
As many as 60 Tory backbenchers could vote against expansion at Heathrow, where options include building a third runway, or lengthening one of the existing runways.
Zac Goldsmith, the Tory MP for Richmond Park, has vowed to resign from the Commons if the government approves a Heathrow expansion.
The
Evening Standard reported on Tuesday that the local Conservative party would back Mr Goldsmith if he stood for re-election as an independent.
Airlines and business groups favour expansion of Heathrow, which offers far more direct connections than Gatwick and handles much more freight.
A final decision on which London airport to expand has been years in the making.
In 2009, former prime minister David Cameron pledged that there would be no new runway at Heathrow. In July 2015, the
Airports Commission chaired by Sir Howard Davies backed a new third runway at Heathrow, but did not rule out the option of expanding Gatwick. Mr Cameron had promised a decision by the end of last year on whether to build a new runway at Heathrow.