This paper extends a random preventive maintenance scheme, called repair alert model, when there exist environmental variables which e ect on system lifetimes. It can be used for implementing age-dependent maintenance policies on engineering devices. The new model is exible to including covariates with both xed and random e ects. The problem of estimating parameters is also investigated in details. To do this, it is assumed that the system lifetime distribution belongs to the log-locationscale family of distributions. A real data set is also analysed on the of the results obtained
