demand increases. Under current strategies of emissions reduction and growth in air transport, air travel in the UK could account for up to 50 per cent of the UK carbon budget by 2050. Industry attempts to address this issue are longer term efforts based on technological and operational improvements, whilst government policy is based on the inclusion of air transport within emissions trading schemes. Critics advocate a shift in government policy to address environmental effects by constraining the growth in demand for air travel, primarily through the use of economic instruments to price air travel less attractively. Local environmental issues include noise and air quality, and the effects of these, particularly in the case of the former, is subject to debate. Government policy generally is that these are local issues best addressed locally, and has introduced legislation designed to facilitate this. Air transport framework Air transport in the United Kingdom is a growth industry. In the period 1981 to 2006 the number of terminal passengers increased by 400 per cent and air transport movements by 250 per cent. Although the transport of freight declined slightly year on year between 2004 and 2006, in the decade since 1996 air freight has increased by 31 per cent. During the period in which government policy was being formulated the number of passengers exceeded 200 million, and in 2006 the industry handled over 236 million passengers (up 3 per cent from the previous year), with nearly 2.4 million air transport movements (up 1.8 per cent). Infrastructure Air traffic services for all UK airspace is provided by National Air Traffic Services (NATS), which also provides air traffic control at 15 airports. The largest airport operator is Heathrow Airport Holdings, owner of six UK airports including Heathrow airport. In some cases airport ownership is in the hands of local government authorities rather than private businesses, and the largest UK owned operator, Manchester Airports Group, operator of Manchester Airport, Bournemouth Airport, East Midlands Airport, and Humberside Airport, is owned by a consortium of 10 Manchester area local authorities. Whilst the number of airports in the UK runs into hundreds, many are smaller aerodromes dealing with general aviation rather than air transport. In terms of the latter, statistics are collected from 59 main airports, and the largest concentration of services is located in the London and South East of England areas. Heathrow is the largest airport in the