The air transport industry has reduced its environmental impact in recent decades mainly through the development and use of new technology, and will continue to do so to ensure, for example, that aviation emissions levels remain modest and that noise levels are constantly improved. Achieving further improvements in environmental performance is a key research and development objective for the industry.

Noise

Industry spends substantial resources on research and development of advanced noise technologies, aiming to achieve ambitious noise reduction goals. The NASA QAT (Quiet Aircraft Technology) programme as well as the European ACARE programme (see information under Emissions), for example, aims to reduce perceived noise levels of future aircraft by 50% up to 2020.

Despite the continuous improvements and research efforts, however, disturbance by aircraft noise continues to be perceived as the single most important environmental issue around airports, particularly in high income countries. Aircraft noise during night hours is increasingly linked to health effects including sleep loss and/or disturbed sleep.

This has resulted in noise-related capacity constraints at many of the world's major airports.  Some airports have reached their noise capacity limits prior to having made full use of their infrastructure, while others have failed to obtain planning approval for further development - simply because of the noise implications from resulting traffic growth. 

To ensure that noise management at airports develops in a balanced and coordinated way, the International Civil Aviation Organization (ICAO) Assembly - which took place in autumn 2001 - adopted a complete international framework for a balanced approach to aircraft noise management, to be applied on an airport by airport basis. This "Balanced Approach" combines four main elements:

• noise reduction at source;
• partial operating restrictions, although not to be applied as a first resort;
• land use planning and management; and
• noise abatement procedures.
  

Emissions

Continuous technology improvement has substantially reduced all emissions from modern aircraft and airlines have been able to make significant progress in the decoupling of environmental impact from economic growth. However, the already high technological and operational standards within the air transport industry make additional improvements increasingly difficult and costly to achieve.

Airframe and engine manufacturers and airlines are participating in research and technology programmes in all fields that improve fuel consumption and, therefore, emissions. The programmes are concerned particularly with aerodynamic improvements, engine integration and airframe weight reduction. Improvements from unconventional designs (such as "blended wing bodies") can also be envisaged, if it can be proven technically feasible, safe and economically viable.

Under the European Union's 6th Framework Programme, ambitious research goals have been based on the objectives of the Advisory Council for Aeronautical Research in Europe (ACARE). They include:

• reducing nitrogen oxides (NOx) emissions of future aircraft by 70% within 10 years, and by 80% within 25 years (using the 1996 ICAO Standard for NOx as the baseline); and
• reducing carbon dioxide (CO2) emissions of future aircraft by 25% and by 50% in the same timeframes (using 1997 subsonic aircraft technology as the baseline).

In the US, similar goals have been set by NASA.

In addition to the use of technical solutions and operational measures as a means of limiting or reducing the impact of aircraft engine emissions, market-based incentives may provide opportunities to limit emissions from aviation at a lower cost and in a more flexible manner than traditional regulatory measures.