Passenger airline tickets could cost 20–30% more on average for shorter flights and 5% more for longer flights if costs such as emissions and noise were accounted for in the price, finds a study by the Dutch Centre for Energy Conservation and Environmental Technology. The study was commissioned by the German environment ministry, which is looking into market-based incentives—such as charges on emissions—for reducing aviation’s rapidly growing environmental impacts. For flights of up to 200 km, local and regional impacts, particularly noise, make up the bulk of the external costs. For flights of 6000 km, greenhouse gases dominate. However, if contrails are formed, as is estimated to occur in 10% of global aircraft kilometers, the climatic impact could be as much as 8 times higher, according to the study. A summary of External Costs of Aviation can be accessed at www.umweltbundesamt.de/aviation.pdf.