In January 2009 the Transport Secretary Geoff Hoon announced that the UK government supported the expansion of Heathrow by building a third 2,200-metre (7,200 ft) runway and a sixth terminal building.[129] This decision followed the 2003 white paper on the future of air transport in the UK,[130] and a public consultation in November 2007.[131] This was a controversial decision which met with widespread opposition because of the expected greenhouse gas emissions, impact on local communities, as well as noise and air pollution concerns.
Before the 2010 General Election the Conservative and Liberal Democrats parties announced that they would prevent the construction of any third runway or further material expansion of the airport's operating capacity. The Mayor of London, Boris Johnson, has taken the position that London needs more airport capacity, but favours constructing an entirely new airport in the Thames Estuary rather than expanding Heathrow.[132] After the Conservative – Liberal Democrat coalition took power, it was announced that the third runway expansion was cancelled.[133] Two years later, leading Conservatives were reported to have changed their minds.[134]
Another proposed plan for expanding Heathrow's capacity is the Heathrow Hub, which aims to extend both runways to a total length of about 7,000 metres and divide them into four so that they each provide two, full length runways, allowing simultaneous take-offs and landings while decreasing noise levels.[135][136]
In July 2013, the airport submitted three new proposals for expansion to the Airports Commission, which was established to review airport capacity in the southeast of England. Each involved the construction of a third runway, either to the north, northwest or southwest of the airport.[137] The commission released its interim report in December 2013, shortlisting the northwest third runway option at Heathrow, extending an existing runway at Heathrow and a second runway at Gatwick Airport. The full report is due to be published in 2015.[138] Following the publication of the interim report, the government confirmed that no options had been ruled out for airport expansion in the southeast, and that a new runway would not be built at Heathrow before 2015