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 adjacent to the airport entrance opened on 1 October 2012; owned by the Stobart Group it has the only rooftop restaurant in Essex. London Southend has been voted the best airport in Britain for three consecutive years by consumer group "Which?" in August 2013, August 2014, and again in September 2015. Southend Airport handles mainly scheduled passenger, charter, cargo and business flights, with some pilot training (both fixed-wing aircraft and helicopter) and private aircraft flying. The airport is run by London Southend Airport Co Ltd, which employs over 150 people directly. Due to expansion, there were over 500 more people