For Al-Cu-Mg, AI-Zn-Mg-Cu and AI-Mg-Li alloys two ageing realization scheme are examined: "usual" ageing. (natural or artificial ageing after solid solution treatment (SST) and quenching to room temperature) and "direct" ageing (quenching from SST temperature to artificial ageing temperature and endurance at this temperature). For the same temperatures two kinds of ageing show the considerable differences in precipitates crystal structures. The explanation of obtained results founded on various influence of two factors, distinguished in cases of the direct or usual ageing, on competing mechanisms of various phases forming: 1) differences in free vacancies concentration and 2) in case of the usual ageing effects of precipitates crystal structure, loaned after quenching at natural ageing, on precipitates structure formed during artificial ageing.