Method for assisting the formation flight of aircraft, the method being implemented by a system in the form of electronic circuitry on board an aircraft acting as a follower aircraft , the method comprising the following steps: - acquiring information relating to a leader aircraft generating a wake vortex inducing an upward airflow, which the system intends the follower aircraft to benefit from; - determining an effect of the wake vortex experienced by the follower aircraft as a difference between measurements, taken by sensors of the follower aircraft , and modelling of the follower aircraft in a wake vortex-free environment; - determining, using a recursive Bayesian filter, an estimated position of the wake vortex on the basis of the information obtained relative to the leader aircraft and of a wake vortex model, and determining an estimation uncertainty of the estimated position of the wake vortex by comparing the effect of the wake vortex experienced by the follower aircraft and a theoretical effect of the wake vortex on the follower aircraft according to the wake vortex model; - determining a potential discomfort window around the estimated position of the wake vortex; and - defining and applying an approach trajectory to the wake vortex; characterized in that the potential discomfort window around the estimated position of the wake vortex is determined as a function of the estimation uncertainty of the estimated position of the wake vortex and the method further comprises the following step: - keeping the follower aircraft outside the potential discomfort window, by controlling a placement of the follower aircraft at a predefined distance from the estimated position of the wake vortex when the dimensions of the potential discomfort window are such that this is allowed, and at a predefined margin from the potential discomfort window otherwise. - acquiring information relating to a leader aircraft generating a wake vortex inducing an upward airflow, which the system intends the follower aircraft to benefit from; - determining an effect of the wake vortex experienced by the follower aircraft as a difference between measurements, taken by sensors of the follower aircraft , and modelling of the follower aircraft in a wake vortex-free environment; - determining, using a recursive Bayesian filter, an estimated position of the wake vortex on the basis of the information obtained relative to the leader aircraft and of a wake vortex model, and determining an estimation uncertainty of the estimated position of the wake vortex by comparing the effect of the wake vortex experienced by the follower aircraft and a theoretical effect of the wake vortex on the follower aircraft according to the wake vortex model; - determining a potential discomfort window around the estimated position of the wake vortex; and - defining and applying an approach trajectory to the wake vortex; characterized in that the potential discomfort window around the estimated position of the wake vortex is determined as a function of the estimation uncertainty of the estimated position of the wake vortex and the method further comprises the following step: - keeping the follower aircraft outside the potential discomfort window, by controlling a placement of the follower aircraft at a predefined distance from the estimated position of the wake vortex when the dimensions of the potential discomfort window are such that this is allowed, and at a predefined margin from the potential discomfort window otherwise. - keeping the follower aircraft outside the potential discomfort window, by controlling a placement of the follower aircraft at a predefined distance from the estimated position of the wake vortex when the dimensions of the potential discomfort window are such that this is allowed, and at a predefined margin from the potential discomfort window otherwise. <EOS>