1. A method for determining a flow in a vicinity of a first aircraft comprising the following steps: measuring one or more flow velocities by one or more sensors on the first aircraft using at least one measuring position of the one or more sensors, each of the one more measured flow velocities being in one measuring direction of the one or more sensors; initializing parameters of a flow model representing a flow, wherein the flow is a wake turbulence of a second aircraft and the flow model is an analytical vortex model; calculating, with an arithmetic unit connected with the one or more sensors, one or more simulated flow velocities at the at least one measuring position according to the flow model representing the flow; comparing with the arithmetic unit the one or more measured flow velocities obtained from said measuring step to the one or more simulated flow velocities obtained from said calculating step; adjusting the parameters of the flow model representing the flow by minimizing a quality function that depends on at least one comparison result of said comparing step to obtain an approximated flow model; repeating said steps of calculating, comparing, and adjusting for one or more iterations; and then determining the flow of the second aircraft in dependency of the approximated flow model.