Boris airport dream left in holding pattern The body investigating the case for expanding UK's airports on Tuesday outlined two ways of giving Heathrow a third runway, but cast severe doubt on proposals for a hub in the Thames estuary. Sir Howard Davies, chairman of the independent Airports Commission, said there was an argument for Heathrow having a third runway by 2030, with Gatwick adding a second by 2050. He rejected suggestions that the commission's decision to study proposals for a new four-runway airport in the Thames estuary - as championed by Boris Johnson, London's mayor - was due to pressure from George Osborne, chancellor. In its eagerly awaited interim report published on Tuesday, the commission shortlisted Heathrow and Gatwick as possible locations for new runways. Expansion options The commission will make a final recommendation following the 2015 general election, after concluding that the southeast of England needs one new runway by 2030 and is likely to require a second by 2050. Heathrow is operating at full capacity on its two runways and Sir Howard said: "It is perfectly possible you do a Heathrow third runway up to 2030 and then when you look at what is needed between then and 2050 it is a Gatwick option - or vice versa." He said the "central issue" in deciding on the location of the next runway, if Heathrow or Gatwick were the only options, would be the sort of airport capacity needed. Heathrow is the country's only hub, where there are significant volumes of passengers who use the airport to transfer from one flight to another, in moves that enable British Airways to provide a broad range of long-haul destinations on a profitable basis. But Heathrow says the UK is missing out on trade because it is struggling to support flights to fast-growing emerging markets. Gatwick is not a hub but instead focuses on so-called origin and destination flying, with travellers typically boarding short-haul flights to holiday destinations in continental Europe. The West Sussex airport says it is best placed to support the most important European aviation trend of the past decade - the rapid growth of low-cost carriers, some of which are starting to do long-haul flying. "The issue is the balance between hub capacity and origin and destination capacity," said Sir Howard. The commission will study two proposals for a new runway at Heathrow costing up to £18bn. The first, by Heathrow Airport Holdings, the hub's owner, would involve building a runway to the northwest of its existing site. However, the commission will also consider a plan by Heathrow hub, an organisation involving Jock Lowe, a former Concorde pilot, to extend the airport's northern runway from 3,900 metres to at least 6,000. This would then be split in the middle to create two runways. At Gatwick, the commission will study the airport's proposal for a second runway south of its existing site that could cost £13bn. Sir Howard raised far-reaching concerns about a new hub in the Thames estuary on the Isle of Grain due to its cost, up to £112bn, and environmental impact. These concerns meant the commission did not include the estuary airport on its shortlist but it will conduct more studies before deciding next year whether to assess the proposal alongside Heathrow and Gatwick. Sir Howard insisted that the commission's decisions were "made by us alone" after questions about whether he was urged by Mr Osborne not to rule out an estuary airport at this stage. The two men met last week, and Mr Osborne asked Sir Howard to keep the estuary proposal alive, said one Treasury official. The chancellor has swung behind the case for Heathrow's expansion over the past three years but does not want a third runway to be an issue in the run-up to the 2015 election. The Conservatives fought the 2010 election on a pledge to scrap the former Labour government's plan for a third runway. Mr Johnson expressed delight that the estuary proposal was "not dead." He said Sir Howard probably began with a shortlist that "didn't include much beyond Heathrow." The London mayor added it was time to stop "fannying around" and come to a final decision on London's future airport needs.