Radiative transfer out of local thermodynamic equilibrium (LTE) has been increasingly adressed, mostly numerically, for about six decades now. However the standard non-LTE problem most often refers to the only deviation of the distribution of photons from their equilibrium i.e., Planckian, distribution. Hereafter we revisit after Oxenius (1986) the so-called full non-LTE problem, which considers to couple and therefore to solve self-consistently for deviations from equilibrium distributions of photons as well as for massive particles constituting the atmospheric plasma.