Lib Dems underline opposition to new London runways
Liberal Democrats have stressed they will not support new runways at Heathrow, Gatwick or Stansted airport.
The party says it is "pushing for a new aviation strategy" which will balance the need for growth with environmental concerns.
It will ask party members to endorse the policy at its annual conference.
A government consultation over expanding airports in south east England has been delayed amid reports of disagreements on how to go ahead.
The Liberal Democrats have long opposed a third runway at Heathrow, the cancellation of which formed part of the coalition agreement.
But Chancellor George Osborne and other Conservative MPs are reported to be warming to the idea - with speculation that this is the reason the consultation has been postponed.
Boris Johnson, who supports a new airport in the Thames Estuary, has accused the government of "pussyfooting around" on airport expansion.
He told the Evening Standard: "The attempt to try and long-grass it for three years into the other side of the election is just not realistic. Totally mad and it won't work."'Environmental threat'
The Liberal Democrats' strategy, which will be debated as a motion at Lib Dem conference, claims that efforts to improve the UK's aviation network are overwhelmingly focused on London and the south east.
It says the party will push for better use of the existing airport capacity in the south east and at regional airports to meet short-to-medium term demand.
A new airport in the Thames Estuary is rejected "firmly", but the party says it wants an "independent evidence-based study" to research alternative locations for a hub airport - which would be environmentally friendly and accessible from all parts of the UK.
It also rejects the "mixed mode" use of runways at Heathrow - where the existing two runways are used for both take-offs and landings.
Lib Dem MP Julian Huppert, chairman of the party's transport committee, said: "Aviation has the potential to become one of the greatest threats to the global environment. Unmitigated expansion of aviation would cause the UK to miss its carbon reduction targets.
"Successive governments have failed to come up with a clear strategy which supports the aviation industry while mitigating its impact on the environment and local residents.
"Enough is enough. The public deserve an airport policy which balances the benefits from aviation with the harms it can do to the environment globally and locally. That is exactly what we'll deliver."
The government's consultation was meant to start in March this year, but was then delayed until the summer, and is now unlikely to go ahead until the autumn.