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 City Airport remotely operated digital control room. Scheduled to be completed in 2018 before being tested for a year, becoming operational in 2019. In 2016, Green Party candidate for the London mayoral election, Siân Berry, proposed the closure and redevelopment of London City airport, citing a number of reasons, including relatively low profit from such a large amount of land, high demand for housing in Greater London and the high levels of pollution generated. Berry also argued that despite more air capacity being needed in the South East of England, the relatively low four million passengers that use London City Airport every