The UK's Airports Commission recently released a new report, which says that building new runways at Heathrow and Gatwick will cost much more than the estimation of bidders.
The Airports Commission has also released its assessment of proposals for additional runway capacity at both the airports and has asked for public comment on the detailed consideration of each proposal.
There are currently three expansion proposals, which consist of the construction of a second runway at Gatwick, a third runway at Heathrow or an extension to one of Heathrow's existing runways.
Initially, other alternatives such as building new airports near Oxford or in Thames Estuary were also under consideration. However, the commission has already rejected these proposals.
While considering proposals, the commission analysed cost, effect of noise, property loss and construction, the economic benefits and their impact on the environment.
Speaking about the report, chairman of the commission Sir Howard Davies said: "Since our interim report last year, we have undertaken a huge amount of work.
"We have carried out a thorough assessment, across a comprehensive range of subjects, looking at the benefits and impacts of each proposal. We have not yet taken a view on which proposal strikes the most effective balance between the assessment criteria. It is important first that we provide an opportunity for this evidence to be examined, challenged and improved.
"This consultation gives everyone with an interest in the issue of airport expansion that opportunity."
The report states that a second runway at Gatwick would be the cheapest option and would cost roughly £9.3bn plus a further £787m from the taxpayer to improve road and rail access. Gatwick had quoted an estimate of £7.4bn for the expansion.
Building a third runway at Heathrow to the north-west of its current site would cost approximately £18.6bn and would also require £5.7bn from the taxpayer to improve surface access.
During the consultation, which will close on 3 February 2015, the commission will hold open discussion sessions for local stakeholders in both the Heathrow and Gatwick areas. The final report will be submitted in mid-2015.
Heathrow Airport also released a statement saying that the commission's report proved that expansion of the airport would lead to an economic benefit of up to £211bn.
Heathrow CEO John Holland-Kaye said: "The Commission has confirmed that only Heathrow can connect all of the UK to global growth, delivering over £200bn to the UK economy and 180,000 jobs while reducing noise for local residents compared to today.
"This shows that Heathrow's proposal is deliverable and is the only way to keep the UK at the heart of the global economy. Now it's time for all those who want a better future for the UK to make their voice heard and back Heathrow."
Image: The Airports Commission has released its report on the feasibility of the expansion of Gatwick and Heathrow Airports and has invited public comment. Photo: courtesy of Heathrow Airport.