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 Southend Airport working at the airport in summer 2012 compared with summer 2011. The airport has been used extensively by British Airways Cityflyer in order to train pilots on their Embraer fleet. Southend Airport has a Civil Aviation Authority (CAA) Ordinary Licence that allows flights for the public transport of passengers or for flying instruction as authorised by the licensee (London Southend Airport Company Limited). Southend Airport has an excellent weather record and is used by airlines as a diversion alternative when adverse weather or incidents close other London airports. Airline ground handling is provided by the Stobart Group owned Stobart Aviation