Aircraft noise disturbs a significant number of people who live close to airports. It is tolerated due to the economic and social benefits those aircraft bring to society as a whole. However, the levels that are tolerated from individual aircraft must reduce, to compensate for increases in numbers of aircraft movements and the desire for an ever-improving environment for all of society's members. The issue is how to achieve that reduction without destroying social and economic benefits of air travel.

This paper reviews some of the options for limiting emissions from aircraft engine exhausts. Its main purpose however, is, to investigate the possibility of a Government-airline partnership and to this end, the issues are reviewed along with a summary of the possible approaches that have been identified to date.

God and Noah were not only the earliest recorded partnership in the history of naval architecture but they were also the most successful. God prepared the requirement and outline specification; Noah responded with a fully engineered design and construction which was not only to survive the worst floods ever seen but was also completed on time. Of course, we know nothing about cost overruns, but I doubt that cost was uppermost in Noah's mind and labour - he used his sons - was in any case cheap!

For the past 50 years civil air transport has been dominated by the combination of the gas turbine and the B-47 airframe configuration. Both these machines owed their creation to WW2 and both represented revolutionary concepts at the time. Oyer the years, the engine and the airframe have undergone considerable detailed refinement. The changes have resulted in very impressive improvements in performance. However, it is now very clear that both are close to some well defined asymptotic limits that bound their performance. The result is that further potential improvements are smaller in percentage terms, become harder to achieve technically and, consequently, come at increasingly higher cost.

A hugely successful global industry has developed around this standard configuration. Increasingly, more and more companies use aircraft and, as their businesses grow, the demand for aircraft and air transport increases. However, the ability of the environment to absorb this growth is beginning to be questioned and new ideas are required if aviation is to be regarded as an unbounded and a truly sustainable activity.

This paper summarises our current understanding about the impact of aircraft emissions on the atmosphere and describes how the UK Natural Environment Research Council (NERC) Upper Troposphere/ Lower Stratosphere (UTLS) Ozone programme is contributing directly to research in this field. Understanding ozone change is a main focus of this research programme.

Ozone is a pollutant at the Earth's surface where it can lead to health problems, is a greenhouse gas and, in the stratosphere, it also shields the Earth from uv radiation. It is known that ozone has been severely depleted in the lower stratosphere (15-20km) over the poles due to increasing concentrations of man-made chlorine and bromine compounds (CFCs etc.). There has also been more limited ozone loss in the mid-latitude lower stratosphere but the reasons for this are less clear because ozone is governed by transport in and out of this region as well as chemistry.

The aviation industry plays a critical role in modern society, supporting global, regional and local economies and facilitating long distance travel for business and leisure. However the environmental impact of the industry is significant and this threatens the sustainability of future growth and the consequential benefits which could arise from it. Technological, operational and infrastructure improvements designed to reduce emissions and noise from aircraft are continually being eroded by the rapid growth of the industry, with the result that the environmental impact of air travel is increasing. Consequently, the sustainable development of the aviation industry will require that in future, technological innovation and fleet replacement continues at a rapid pace and that the highest priority is given to achieving a ‘step change’ in aircraft technology.