sum mo mc pfq moreover the relation r of the type dxi k dm is determined linking the variation in position dxi of the center of gravity of the aircraft 1 to the variation in weight of fuel dm inside the tail tank 22 in this relation r the letter k designates a constant representative of the distance between the position xo and said tail tank 22 the graphical representation of this relation r in the chart of fig4 is a straight line similar to the linear characteristic 29 of fig5 represented in fig4 is the corresponding characteristic 31 passing through the point t defined above in accordance with the present invention weights of fuel whose sum constitutes a provisional loading weight mp which is less than the weight of fuel pfq necessary for the accomplishment of the mission and which added to the cargo weight mc causes the center of gravity of the aircraft 1 to go from the position xc to a provisional position xp are poured into said tanks 11 to 19 and possibly 22 this provisional loading weight mp is chosen to correspond to the intersection between the straight line 28 relating to the position xp not represented of the center of gravity and the linear characteristic 31 of course during this loading operation similar weights of fuel are poured into symmetric tanks each weight of fuel added to the central tank 11 and possibly to the tail tank 22 and the weights of fuel added symmetrically to the symmetric tank pairs are associated in the chart of fig4 with linear characteristics 32 33 34 etc respectively similar to the linear characteristics 29 or 30 as a function of the position of the corresponding tanks with respect to xo these characteristics form a broken line.