The door has been left open for both Glasgow and Edinburgh airports to build new runways by 2020.
Air passenger figures are continuing to rise
The decision was revealed when the government published its white paper on aviation, outlining a 30-year strategy for Britain's airports.
Transport Secretary Alistair Darling said that land at the sites should be safeguarded for possible expansion.
Both Glasgow and Edinburgh want a new runway to cope with increasing passenger numbers.
The two airports, along with Aberdeen, Inverness and Prestwick, could be handling up to 50m passengers a year by 2030.
That compares to 16m passengers in 2000.
Mr Darling told the House of Commons it was expected that additional runway capacity would be needed in the central belt probably by about 2020.
The announcement seemed to favour a new runway for the capital but did not rule out expansion at Glasgow Airport.
"We propose to safeguard land at Edinburgh for a second runway together with the associated expansion of terminal buildings," he said.
"We also recommend that consideration is given to protecting land at Glasgow for a possible new runway and we also support safeguarding land for terminal expansion there.
"The Scottish Executive has published plans to improve service access to both Glasgow and Edinburgh airports."
The white paper also sets out proposals to allow continued growth at Aberdeen, Inverness and Prestwick, but the case for a new airport in central Scotland was ruled out.
Plans cover air travel over the next 30 years
Mr Darling added that proposals were being put forward to impose public service obligations in defined circumstances to protect landing slots for key services to Heathrow and Gatwick.
However, the Scottish Green Party's Robin Harper warned that increased air travel posed a growing ecological threat.
"You either have an environmental policy or you don't," he said.
"If we go down the route of doubling air transport by 2020 we will have taken one step forward with our other environmental policies and two steps backwards by allowing air transport to expand unlimited."
And Friends of the Earth Scotland said any proposals for new runways must take second place to curbing the environmental damage caused by air travel.
BAA chief executive Mike Clasper said he was pleased that the government had taken a long-term view.
Mr Clasper, whose company runs Glasgow, Edinburgh and Aberdeen airports, added: "We advised the government to safeguard land at both Edinburgh and Glasgow.
"BAA will now work within the new policy framework to develop its Scottish airports to their full potential."
The government believes there is a good economic case for phased development of extra runway capacity at Edinburgh, with the possibility of Glasgow doubling its present terminal capacity, although it said there was no clear case for an additional runway at the moment.
Other proposals include the possible extension of the runway at Aberdeen and a runway extension and development of additional terminal capacity in Inverness by 2015.
Mr Darling also announced an extra runway at Stansted Airport in Essex to cope with passenger growth in the London area.