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Atmospheric aerosols represent an important but uncertain component of the atmosphere, which are known to affect the Earth's radiative budget by scattering and absorbing solar and terrestrial radiation, and by influencing the optical properties and lifetime of clouds. Organic aerosols are a ubiquitous feature of atmospheric composition around the globe, yet also represent a significant source uncertainty with regard to the understanding of aerosol behaviour and their representation m regional and global models. Presented here are aircraft measurements of organic aerosols arising from biomass burning and biogenic production over West Africa; the predominant sources of submicron aerosols during the dry and wet seasons in a region which has received comparatively little study in the literature. Measurements were taken usuig an Aerodyne Quadrupole Aerosol Mass Spectrometer (Q-AMS) installed on the UK Facility for Atmospheric Measurements (FAAM) aircraft. The physical and chemical properties of biomass burning aerosols were investigated on a continental scale, with particular focus on the evolution of these characteristics as the aerosols aged during transport from the source region. Systematic evolution of the chemical composition of aerosols was observed and aerosols became increasingly oxygenated with increasing distance from source. Emission ratios were estimated for black carbon and organic carbon, which compare well with previous results though the estimates made here are on regional scales rather than from single fires. Evolution of the particle size distribution was dominated by coagulation rather than condensation, and negligible secondary organic aerosol (SOA) production was observed. The chemical evolution of biomass burning aerosols without an increase in mass from secondary production appears to be a consistent finding for biomass burning aerosols, when the same analysis was completed for biomass burning emissions from other regions.