Now is the time to bring the UK's international aviation and shipping emissions formally within the UK's net-zero target.
The growth in demand for flights must be curbed to tackle greenhouse gas emissions as part of the UK's climate targets, government advisers have said.
Extra levies on those who fly frequently, reformed taxes or a price on carbon and management of the amount of airport capacity in the UK are among the potential measures suggested by the Committee on Climate Change.
They are needed to limit the growth in demand for flights to no more than 25 percent above current levels by 2050 as part of efforts to reduce the UK's emissions to net zero by mid-century, the committee said.
And it warned the government it needed to assess its strategy for providing airport capacity in the context of cutting emissions, and make sure investments make "economic sense" in a net-zero world.
Current planned additional capacity in London, including a third runway at Heathrow "is likely to leave at most very limited room for growth at non-London airports", the committee said.
The recommendations come in a letter from Lord Deben, the committee's chairman to Transport Secretary Grant Shapps on including international aviation and shipping emissions in the UK's targets to cut greenhouse gas emissions to zero overall by 2050.
The letter said aviation was likely to be the largest emitting sector in the UK by 2050, even with strong progress on technology to provide greener fuels and limiting demand for international flights.
Including the emissions in the legally-binding net zero target emissions will show the scale of deployment needed for measures to remove carbon dioxide from the atmosphere to offset the emissions caused by flying.
As far as shipping is concerned, the committee said net zero was likely to be feasible and cost-effective through use of alternative fuels, such as hydrogen or ammonia.
Chris Stark, CCC chief executive, said: "Now is the time to bring the UK's international aviation and shipping emissions formally within the UK's net-zero target.
"These are real emissions, requiring a credible plan to manage them to net-zero by 2050.
"Their inclusion in the UK target will complement international approaches and increase confidence that the government is prioritising their reduction, ensuring the net-zero target covers all of the UK's emissions.
"As the UK prepares to host the next major climate summit in 2020, we are well placed to show global leadership on this fundamental issue of international concern."
Leo Murray, director at campaign group 10:10 climate action, said aviation had been given a "free ride" in climate policy for too long, with politicians putting it in the "too hard" box.
He said the government was talking up electric planes, which should be an innovation priority, but the potential for technology to contribute to carbon cuts in a short time frame was limited.
"The CCC make it very clear that growth in demand for flights from UK airports cannot continue unchecked. That's why we need to introduce a frequent flyer levy.
"Most of the environmental damage from air travel is caused not by annual family holidays but by very frequent leisure flights by those at top end of the income spectrum.
"A frequent flyer levy is the fairest and most effective way to keep aviation emissions within safe limits, at the same time as protecting access to some air travel for all," he said.
Dr Doug Parr, chief scientist for Greenpeace UK, said the Government's current aviation strategy is incompatible with the net zero target, "and must be revised".
"The new strategy must focus on restricting demand growth, and will either require Heathrow's third runway being cancelled, or capacity restrictions on other airports to balance Heathrow's expansion."
A Department for Transport spokeswoman said: "The fight against climate change is the greatest and most pressing challenge facing the modern world and this Government recognises that aviation and shipping have a crucial role to play in tackling it.
"The government has already made clear its commitment to zero emission shipping in the Clean Maritime Plan, which was published earlier this year.
"We are also committed to setting a clear ambition for the aviation sector and will carefully consider the advice of the Committee on Climate Change when we publish our position on aviation and climate change for consultation shortly."
Emily Beament is the PA environment correspondent.