Technological developments and radical innovations Over the past fifty years, fuel consumption per passenger kilometre flown has decreased significantly. This makes flying a very efficient way to travel. The noise produced by aircraft has also decreased dramatically. However, due to the large number of flights worldwide, there is a need for a further reduction in climate impact. The following challenges show that this is a difficult task: click here for full text https://www.nlr.org/focus-area/programmes/programme-climate-neutral-aviation/technological-developments-and-radical-innovations/