A procedure and device optimize the quantity of fuel transferred on an aircraft during at least one in-flight fuel transfer. The optimization device includes a section that makes a prediction to determine a first quantity corresponding to the quantity of fuel remaining on board the aircraft at a first flight point in the flight plan of the aircraft, taking into account the current status of the aircraft and the current flying conditions. The device further includes a section that makes an estimation to determine a second quantity corresponding to the quantity of fuel enabling the aircraft to fly from the first flight point to a second flight point later in the flight plan. The device further includes a section that determines, from the first and second quantities, a third quantity corresponding to the quantity of fuel to be transferred at the first flight point. The device further includes a display that presents the third duly determined quantity to at least one pilot of the aircraft.