Airports Commission reveals expansion shortlist
New runways at Heathrow and Gatwick are among the options that have been short-listed by the Airports Commission for expanding UK airport capacity.
The three short-listed options include adding a third runway at Heathrow, lengthening an existing runway at Heathrow, and a new runway at Gatwick.
The commission, led by businessman Sir Howard Davies, has also not ruled out a new airport in the Isle of Grain.
However, it says it will need further analysis before deciding.
A final report is due by the summer of 2015.
Sir Howard was asked in 2012 to investigate the options for expanding the UK's aviation capacity and try to come up with a plan.
He said the Commission's analysis showed one net additional runway was needed by 2030.
"The capacity challenge is not yet critical, but it will become so if no action is taken soon," he added.
The Mayor of London, Boris Johnson, has said that putting a new runway at Heathrow would be a "catastrophe".
Following the commission's report, Mr Johnson said he continued to support the creation of the Isle of Grain airport in north Kent.
"A new airport in the inner estuary is the only credible hub option left. By keeping it on the table, Davies is saying you have a choice - between a damaging U-turn or a radical new vision for expansion," he said.
The commission said it would undertake further study of the Isle of Grain option in the first half of next year, before deciding whether it offers "a credible proposal for consideration alongside the other short-listed options".
But supporters of Heathrow's expansion say it will be quicker and cheaper than other options and will help to maintain the UK as an international aviation hub.
Heathrow's owners submitted evidence to the commission arguing that a new runway could be in place by 2029, allowing 260,000 more flights.
Colin Matthews, Heathrow chief executive, told the BBC: "The case for Heathrow is strong. It's important that businesses can get around the globe to where economies are growing."
Heathrow is one of the world's busiest hub airports, handling 70 million passengers in 2012. A third of those travellers were transit passengers transferring to other flights.
But the airport operates at 98% of its capacity.
When the coalition government came to power in 2010, it scrapped the former Labour government's plan for a third runway at Heathrow.
The government said on Monday that it had not ruled out any options when it came to airport expansion in the south-east of England.
On Sunday, Transport Secretary Patrick McLoughlin said that the government would stick to its pledge not to build a new runway at Heathrow before 2015.
He told the BBC: "We will not be building a third runway in this Parliament. We will stick by our manifesto commitment."
The commission has not shortlisted proposals for expanding Stansted or Birmingham, but said there was likely to be a case for considering them as "potential options" for any second new runway by 2050.