More calls have been made within the Conservative party for its leadership to rethink the policy opposing a third runway at Heathrow Airport.
Tory MP Tim Yeo has said it should go ahead, two days after Housing Minister Grant Shapps hinted a future Tory government could consider the option.
The coalition agreement rules out any expansion before the next election and Labour also currently opposes it.
Mr Shapps told the Daily Telegraph that "all options should be considered".
He told the newspaper on Saturday: "I back the Chancellor's position to the hilt when he said in the Budget we clearly need to review the airport capacity in the South East. All the options need to be considered while being mindful of our election manifesto."
Asked by the BBC whether he believed the Heathrow expansion could take place after the next general election, in 2015, Mr Shapps said: "These things need to be considered in due course."
Speaking to the BBC Radio 4's Today programme on Monday, Mr Yeo said the issue "was a race in which Britain is now falling behind and we need to get back into it".
"Airlines are among the people who're pushing for this now very badly-needed expansion, so that we don't continue to lose out against airports like Frankfurt and Charles de Gaulle, both of whom have twice as many destinations in China, twice as many flights going to China," he said.
The former Labour chancellor, Alastair Darling, also told the programme the expansion at Heathrow needed to go ahead.
"The whole point about Heathrow is that it has more destinations than most other airports in the world. And the reason that it works is that if you fly into Heathrow you can go to most parts of the world.
"You can't have two hubs with one half of the world in one place, and one half in the other place. It simply doesn't work like that. Now, the advantage of Heathrow is it is there now, we can't go on putting this decision off," he said.
Transport Secretary Justine Greening - whose Putney constituency is on the Heathrow flightpath - has been a vehement campaigner against a third runway at the airport.
Some residents, who live under the flight path and are opposing the new runway plan, say better use could be made of existing airport capacity.
John Stewart, chairman of the Heathrow Association for the Control of Aircraft Noise, told BBC Radio 5 live's Stephen Nolan: "At the moment, the Department for Transport's own figures show that we have sufficient capacity, even in London and the South East, until almost 2030.
"So we have got time to look and see what we need. Justine Greening is quite right to say 'let's not rush into this'."
Jane Thomas, a campaigner at Friends of the Earth, said the business case for expansion had also not been made.
She said the government needed to take a "strong and clear leadership over aviation", which meant including aviation and shipping in the UK carbon budget.
"The Tories were emphatic that there would be no Heathrow expansion in 2010, and we still expect that commitment," she said.
The Mayor of London, Boris Johnson, who also opposes expansion at Heathrow, has campaigned for a new airport in the Thames Estuary.
A £50bn project to build an airport east of London has been put forward by architect Lord Foster.
A consultation on the future of air capacity in south-east England has twice been delayed by the government.