Pollutant emissions

Large aero engines are subject to certification and must comply with the relevant limits for air pollutants emissions. However, thanks to the enormous improvements made in engine efficiency, fuel combustion leaves hardly any residues nowadays. Nevertheless, nitrogen oxides remain a problem and the limits have been gradually tightened over the past ten years.

Further information

https://www.bazl.admin.ch/content/bazl/en/home/specialists/regulations-and-guidelines/environment/pollutant-emissions.html