The environmental effects of aviation in the United Kingdom are increasing due to the increasing demand for air travel in the country. In the past 25 years the UK air transport industry has seen sustained growth, and the demand for passenger air travel in particular is forecast to increase more than twofold, to 465 million passengers, by 2030. Two airports; London Heathrow and London Gatwick, are amongst the top ten busiest airports in the world for international passenger traffic. Whilst more than half of all passengers travelling by air in the UK currently travel via the five London area airports, regional airports have experienced the most growth in recent years, due to the success of 'no-frills' airlines over the last decade. The ability of the existing airport infrastructure to meet forecast demand is limited, and government policy published in 2003 supports the development of additional airport capacity by 2030 to address this. The strategy is generally based on making the best use of existing facilities, although an additional five new runways nationwide are considered to be necessary, three of them at the London airports of Stansted, Heathrow and, towards the end of the timeframe involved , Gatwick. This policy is designed to be a balanced and measured approach to the future of the air transport industry; one that recognises both an economic advantage in providing for growth in demand for air travel and also the need to address the consequent environmental effects. The strategy has been criticised by the House of Commons Environmental Audit Select Committee, by environmentalist and campaign groups, and in research papers, for implementing a predict and provide model that overstates the economic advantages whilst paying insufficient heed to the environmental consequences. Support for airport expansion is based on an economic case that regards the air transport industry not only as an important industry in its own right, but also as a facilitator of growth for the economy as a whole. One study predicts that the government's strategy will realise an additional £13 billion per annum in Gross Domestic Product (GDP) by 2030. Another study which is critical of the government approach, and which favours addressing environmental effects through increased taxation of air transport, indicates a negative economic benefit resulting from airport expansion. In 2006 the industry was responsible for over 6 per cent of all UK carbon emissions, a figure that is set to rise as