2% of the CO2 generated by humans is due to air transport. The biggest costs for Airlines are coming from fuel, so they are constantly trying to implement fuel efficiency improvements. These include experimenting with less weight, different devices and flying technics as well as sustainable alternative aviation fuels, which are already used on a small increasing scale. Several NGOs and organisations of air transport identified the airlines working the most towards alternative fuels and sustainability, which are Lufthansa, KLM and Virgin Airlines.