Air navigation service providers ensure safe and efficient flight operations by managing the separation of aircraft. Following a sharp downturn due to the COVID pandemic, air traffic demand is currently recovering. It may be expected that the increasing number of flights directly affects the environment. Based on the STATFOR traffic forecasts from autumn 2021, we use regression analyses to predict delays, emissions, and environmental costs for the years 2021 to 2027. We will show that the uncertainty of traffic demand has significant consequences for environmental performance indicators.