Economy of London project is construction of 42 km (26 mi) of new tunnels connecting stations in central London including a branch to Canary Wharf in east London. It is Europe's biggest construction project with a £15 billion projected cost. An additional line, Crossrail 2, has been proposed. London is served by six international airports which are the world's busiest city airport system by passenger traffic. These are Heathrow, Gatwick, Stansted, Luton, London City, and Southend. There are a number of proposals for expanding airport capacity for London including expansion of London Heathrow Airport and expansion of Gatwick Airport. The principal argument in
London Britannia Airport many years. The idea was revived in 2008 by the Mayor of London, Boris Johnson, to be located towards the Shivering Sands area, north-east of Whitstable. The deputy mayor, Kit Malthouse, had supported a Thames estuary airport since before taking office. In November 2008, the mayor appointed Doug Oakervee (executive chair of Crossrail) to lead the Greater London Authority's preliminary feasibility study, which determined in October 2009 that there is "no logical constraint" to the plan. The London Britannia Airport name was adopted for the latest iteration of the idea presented in November 2013. This proposal would cost £47.3 billion