<p>Aircraft engines are a unique source of carbonaceous aerosols in the upper troposphere. There, these particles can more efficiently interact with solar radiation than at ground. Due to the lack of measurement data, the radiative forcing from aircraft particulate emissions remains uncertain. To better estimate the global radiative effects of aircraft exhaust aerosol, its optical properties need to be comprehensively characterized. In this work we present the link between the chemical composition and the optical properties of the particulate matter (PM) measured at the engine exit plane of a CFM56-7B turbofan. The measurements covered a wide range of power settings (thrust), ranging from ground idle to take-off, using four different fuel blends of conventional Jet A-1 and Hydro-processed Ester and Fatty Acids (HEFA) biofuel. At the two measurement wavelengths (532 and 870 nm) and for all tested fuels, the absorption and scattering coefficients increased with thrust, as did the PM mass. The separation of elemental carbon (EC) and organic carbon (OC) revealed a significant mass fraction of OC (up to 90 %) at low thrust levels, while EC mass dominated at medium and high thrust. The use of HEFA blends induced a significant decrease in the PM mass and the optical coefficients at all thrust levels. The HEFA effect was highest at low thrust levels, where the EC mass was reduced by up to 50–60 %. The variability in the chemical composition of the particles was the main reason for the strong thrust dependency of the single scattering albedo (SSA), which followed the same trend as the OC fraction. Mass absorption coefficients (MAC) were determined from the correlations between aerosol light absorption and EC mass concentration. The obtained MAC values (MAC<sub>532</sub> = 7.5 ± 0.3 m<sup>2</sup> g<sup>−1</sup> and MAC<sub>870</sub> = 5.2 ± 0.9 m<sup>2</sup> g<sup>−1</sup>) are in excellent agreement with previous literature values of absorption cross section for freshly generated soot. The Simple Forcing Efficiency (SFE) was used to evaluate the direct radiative effect of aircraft particulate emissions for various ground surfaces. The results indicate that aircraft PM emissions over highly reflective surfaces like snow or ice have a substantial warming effect. The use of the HEFA fuel blends decreased PM emissions, but no changes where observed in terms of EC/OC composition, optical properties and forcing per mass emitted.</p>