Abstract: The invention relates to a process for the manufacture of a mixture of liquid nitrogen and liquid oxygen, the proportions of which are approximately those of liquid air, according to which: first, an amount AN2 of liquid nitrogen (10) is transferred (11) into a mixing tank (30); secondly, an amount AO2 of liquid oxygen (20) is transferred (21) into the mixing tank (30), the amounts AN2 and AO2 making it possible to reconstitute, in the mixing tank, a primary mixture within a given range of oxygen content; the mixing tank is kept on hold for a resting period which promotes the stabilization of the mixture formed, making it possible to obtain, on conclusion of this resting period, the desired mixture.