The invention relates to a method for aligning an inertial navigation system borne by a static or quasi-static carrier, wherein: a plurality of alignment processes that are dimensioned for a plurality of amplitudes of movements of the carrier are implemented simultaneously with different alignment observation durations; a minimum observation duration that corresponds to the alignment observation duration for which the consistency of the alignment information obtained by means of alignment processes dimensioned for a given movement amplitude of the carrier is determined; and the alignment information is determined depending on alignment information determined for this minimum observation duration. The invention also relates to an associated inertial navigation system.