A method for securing the operation of a synthetic vision system of an aircraft, the synthetic vision system providing a synthetic display of the outside environment of the aircraft according to a field of view, using first projection rules generated as a function of first measurements of the current position and the current attitude of the aircraft; the method comprising the following steps: - determining at least one control object in the field of view of the synthetic vision system and for the or each control object, determining at least one control point belonging to that control object, the or at least one of the control objects corresponding to a fictitious object in the outside environment of the aircraft, the fictitious object being an object defined in the terrestrial reference frame but not present in the external environment of the aircraft, the or each control object being fixed in an earth-based coordinate system or is defined relative to the aircraft, on a longitudinal axis of the aircraft and in front of the latter; - verifying the coherence of the display of the synthetic vision system, said display comprising an outline of the or each determined control object by using the first projection rules, said verification step comprising the following sub-steps carried out for at least one control point: + recovering a first position corresponding to the displayed position of this control point on the corresponding outline of the display of the synthetic vision system; + determining a second position of this control point on the display of the synthetic vision system, by using second projection rules generated independently of the first projection rules, the second projection rules being generated from second measurements of the current position and the current attitude of the aircraft, the first measurements and the second measurements being provided by different and independent sensors (27, 37); + comparing the first and second positions, the display of the synthetic vision system being inconsistent when the second position differs from the first position by at least a predetermined threshold. - determining at least one control object in the field of view of the synthetic vision system and for the or each control object, determining at least one control point belonging to that control object, the or at least one of the control objects corresponding to a fictitious object in the outside environment of the aircraft, the fictitious object being an object defined in the terrestrial reference frame but not present in the external environment of the aircraft, the or each control object being fixed in an earth-based coordinate system or is defined relative to the aircraft, on a longitudinal axis of the aircraft and in front of the latter; - verifying the coherence of the display of the synthetic vision system, said display comprising an outline of the or each determined control object by using the first projection rules, said verification step comprising the following sub-steps carried out for at least one control point: + recovering a first position corresponding to the displayed position of this control point on the corresponding outline of the display of the synthetic vision system; + determining a second position of this control point on the display of the synthetic vision system, by using second projection rules generated independently of the first projection rules, the second projection rules being generated from second measurements of the current position and the current attitude of the aircraft, the first measurements and the second measurements being provided by different and independent sensors (27, 37); + comparing the first and second positions, the display of the synthetic vision system being inconsistent when the second position differs from the first position by at least a predetermined threshold. + recovering a first position corresponding to the displayed position of this control point on the corresponding outline of the display of the synthetic vision system; + determining a second position of this control point on the display of the synthetic vision system, by using second projection rules generated independently of the first projection rules, the second projection rules being generated from second measurements of the current position and the current attitude of the aircraft, the first measurements and the second measurements being provided by different and independent sensors (27, 37); + comparing the first and second positions, the display of the synthetic vision system being inconsistent when the second position differs from the first position by at least a predetermined threshold.