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 Biggin Hill Airport that the granting of a 125-year lease would enable more control to be retained than an outright disposal of the freehold or by a transfer to a local authority company with an uncertain future. In May 1994, the airport was leased to Biggin Hill Airport Limited ("BHAL") for 125 years. BHAL is a subsidiary of Regional Airports Ltd. who previously owned London Southend Airport. Meanwhile, the Officer and Aircrew Selection Centre moved to RAF Cranwell in 1992, marking the end of active RAF involvement. In 2001, the London Borough of Bromley as freeholder of the airport succeeded in an action