Mean vertical profiles of CO (left panel) and O3 (right panel) for concomitant take-offs and landings over a time window of 30 min. The shaded area shows the uncertainty on the mean at a 95% confidence level (±2 standard deviations normalized by the square root of the number of points). The differences of CO mixing ratios are small (~5%) and statistically insignificant below 300 m ASL, and moderate (10–15%) and slightly significant between 300 and 900 m ASL. Above, the differences are low and insignificant. A very good agreement is found for O3. DOI: https://doi.org/10.1525/elementa.280.f10