A final decision on whether to build a new runway at Heathrow Airport has been put off until at least next summer "subject to further consideration on environmental impacts and the best possible mitigation measures", the Government said.
After discussion of the controversial issue by Prime Minister David Cameron and senior Cabinet ministers, Transport Secretary Patrick McLoughlin said there was a "clear" case for airport expansion "but it's vitally important we get the decision right so that it will benefit generations to come".
He said ministers - who had promised a decision by the end of the year - would "undertake more work on environmental impacts, including air quality, noise and carbon" and "continue work on all the shortlisted locations" - two at Heathrow and one at Gatwick.
The Davies Commission concluded in July that a third runway at Heathrow was the best option - if a string of measures were put in place to deal with noise and pollution - but left open the option of expanding capacity at Gatwick instead.
Critics say the delay will harm the economy and is a politically-inspired move to avoid damaging resignations by high-profile Tories - including London mayoral candidate Zac Goldsmith, who has vowed to quit as an MP if Heathrow is approved.
The contest to success current City Hall incumbent Boris Johnson - himself implacably opposed to the third runway - will take place in May, with Labour candidate Sadiq Khan also against Heathrow expansion.
In a statement issued after the meeting of the Cabinet airports sub committee, the Government said it backed the Commission's call for more runway capacity by 2030 but faced a "complex and challenging decision on delivering this".
"The Government will undertake a package of further work and we anticipate that it will conclude over the summer. The Government will do this quickly so that the timetable for delivering capacity set out by the Airports Commission can be met," it said.
"The Airports Commission's air quality analysis will be tested using the latest projected future concentrations of nitrogen dioxide.
"The next step is to continue to develop the best possible package of measures to mitigate the impacts on local people and the environment.
"This will include a package for local communities to include compensation, maximising local economic opportunities through new jobs and apprenticeships, and measures to tackle noise.
"More work will be done on environmental impacts. The Government expects the airports to put forward ambitious solutions."
Mr McLoughlin said: "The case for aviation expansion is clear - but it's vitally important we get the decision right so that it will benefit generations to come. We will undertake more work on environmental impacts, including air quality, noise and carbon.
"We must develop the best possible package of measures to mitigate the impacts on local people. We will continue work on all the shortlisted locations, so that the timetable for more capacity set out by Sir Howard is met.
"At the first opportunity I will make a statement to the House to make clear our plans."