Using band-structure calculations within the FLAPW (Full-Potential Linearized Augmented-Plane-Wave) model, information is obtained regarding the energy, charge and spatial characteristics of aluminium nitride and its solid solutions with oxygen and aluminium. As established, the formation of these solutions is accompanied by a reduction in electron density in their interatomic regions. The accompanying decrease in the covalence of interatomic interactions leads to both a reduction in binding energies and an increase in the volumes of elementary cells within the compounds. The transition from aluminium nitride to its energetically ‘nearest’ oxide is accompanied by a decrease in binding energy by 1.25 eV, which corresponds to over 14.5$\cdot10^{3}$ K on the temperature scale. This correlation underscores the high resistance of aluminium nitride to oxidation processes. The formation of an alloy with aluminium incorporation becomes even less likely due to the larger decrease in binding energy by 2.84 eV.