Tory MP Zac Goldsmith has urged David Cameron to "get off the fence" over a third runway at Heathrow and signal whether or not the Conservatives will go into the next election in favour of expanding the airport.
His comments on Wednesday morning follow speculation that the Cabinet reshuffle was designed in part to pave the way for a major political row over the proposed runway, which the Tories cancelled when they came to power in 2010.
On Tuesday Justine Greening lost her job as transport secretary and was sent to the relatively lower-profile Department of International Development while transport minister Theresa Villiers was moved to the Northern Ireland Office. Both women are fierce opponents of building the runway, which would see about 700 homes in west London demolished.
Goldsmith told Today on BBC Radio 4: "It's impossible to pretend this isn't a sign that you open the door to at least the possibility of a third runway."
"Have they changed their mind on Heathrow, yes or no?" he asked.
Goldsmith represents Richmond Park in south west London, a part of the city whose residents can see and hear low-flying Heathrow planes for up to 18 hours a day.
He has threatened to resign as an MP if Cameron comes out in favour of a new runway. The PM fuelled speculation that the Tories could U-turn on their Heathrow policy in June when he refused to rule one out in an answer to Goldsmith in the Commons at PMQs.
There is no suggestion that the government would U-turn and agree to a third runway before the next general election but there is speculation that the Conservative party will signal a change of policy in its next manifesto.
The Labour party - despite signing off the runway before the last election while in government - is likely to be now opposed to Heathrow expansion, as will the Lib Dems.
The government is launching a wide-ranging consultation on Heathrow which is likely to conclude sometime next year. But speaking on Wednesday morning Mayor of London Boris Johnson told Sky News: "There's lots of stuff been coming out of Whitehall to suggest that a U-turn is in progress and they want to build a third runway at Heathrow.
"All the pressure from businesses to do the third runway, that's where the Treasury seems to be focusing its hopes," he said.
"What we need to do now is to end the uncertainty over Heathrow and say 'no folks it is all right, the policy is as it has been which is to say no to a new runway both now and in the future - ie in the next two and a half years."
Business leaders and aviation experts have warned that Heathrow risks losing its "hub status", as other major airports in France, Germany and the Netherlands have the capacity to open up routes to emerging markets in China, India and Brazil.
Airports in Frankfurt and Paris have four runways each, while Schiphol in Amsterdam has six of them. Heathrow's two runways are running at near capacity.
The crisis at the UK's largest airport is temporarily being eased by allowing more simultaneous take-offs and landings on each runway, so-called "mixed mode". The government has allowed limited trials of the more intense use of the runways since last year, but this gives residents near Heathrow less respite from the roar of jet engines on take-off.
Business leaders say that it would take too long to build a new airport elsewhere, and by the time it was finished the UK aviation industry would have lost out to rivals on the near continent.
Everyone accepts that Heathrow was built in the wrong place, too close to central London and in a fog-prone area, but aviation experts believe in the medium term expanding the airport is the only way to keep up with European rivals.
Grant Shapps, the new Chairman of the Conservative party, insisted on Wednesday morning that the government's policy on Heathrow hadn't changed, but insisted that airport capacity in the south-east of England remained a pressing concern that needed to be addressed.