The government will decide whether to accept a recommendation by the Airports Commission, led by Sir Howard Davies, to increase capacity at Heathrow airport by building a third runway "by the end of the year", the Prime Minister said today.
Although David Cameron ducked the question of whether he backed the plan during Prime Minister's Questions, he promised the government would decide one way or the other by the end of the year.
In a speech following PMQs, transport secretary Patrick McLoughlin seemed to hint that a decision could come as soon as September.
"This is a vital moment for the future of our aviation industry," he said.
"All those with an interest in this important question are expecting us to act decisively."
McLoughlin's statement came as businesses urged the government to make a decision on an expansion as soon as possible.
"The government must commit to the decision now, and get diggers in the ground... by 2020," said John Cridland, the outgoing director general of the CBI.
Simon Walker, the Institute of Directors' director general, added: "There can now be no further delay form politicians... if ministers do not proceed with all possible speed it will send a clear signal that the UK is not interested in being a modern, outward-looking nation."
However, there is mounting evidence of a split in the cabinet over the issue. While Cameron himself and others such as chancellor George Osborne have kept schtum on the subject, others, such as Boris Johnson, have been vocal in their opposition.
This morning Johnson, who was in May elected as MP for Uxbridge - directly under Heathrow's flightpath - scoffed at the plans.
"It's not going to happen," he said in an interview with the BBC this morning.
"This is the sort of thing you could possibly have got away with in China in the 1950s."