The system comprises an outer container which is fixed, directly and fully, in the hold of the transport aeroplane (AC), and in which there is an inner container that can be moved longitudinally and brought from a first or carrying position in which it is situated fully inside the outer container into a second or off-loading position (P2) in which it is longitudinally offset towards the rear of the aircraft (AC) so that a part of the inner container is then situated outside the transport aeroplane (AC).