Over the last 40 years, the steady increase in the number of flights and urban developments around airports has greatly increased the exposure of the public to aircraft noise. This is now seen as a major problem to be solved if the current growth in air transport is to be sustained. Some improvements might be realised in the short-term through changes in operational procedures (without any change in aircraft and air traffic control systems), while new equipment may help over the next five to ten years (if developed to meet noise criteria).