Air traffic is one of the main sources of man's impact on the atmosphere. Emission of soot particles by airplanes has a significant influence on the climate. Soot particles affect climate directly by the formation of longlived contrails and indirectly by acting as nuclei for cirrus clouds formation. There are some experiments focused on ice nucleation on soot, yet no definitive conclusion has been reached. Most likely one of the reasons behind these discrepancies resides in the different physico-chemical properties of soot particles produced in different conditions, e.g. with respect to fuel or combustion techniques. The aim of our work is to investigate the influence of the combustion conditions on the structure of generated soot. We have used Raman microscopy (514 and 785 nm excitation) to study the spectral parameters of the first-order Raman band of various soot samples, collected from three different sources in the frame of the MERMOSE project (http://mermose.onera.fr/): PowerJet SaM-146 turbofan (four engine regimes), CAST generator (propane fuel, four different global equivalence ratios), and Kerosene laboratory flame. Figure 1 shows typical Raman spectra recorded for some of these samples.