Flutter instability is a typical aerodynamic vibration phenomenon of slender elastic bridges. The sensitivity for flutter can be predicted by determining the so-called nutter derivatives from the small-scale model of the bridge. This work investigates an elastic supported two d.o.f. bridge section model which can move vertically and rotate around a horizontal axis. These movements correspond to the bending and torsional vibrations of the bridge. The linearised equations of motion is assumed to be known, thus, the aerodynamic forces can be determined from wind-tunnel experiments. These forces are assumed as linear functions of the generalised coordinates and their time-derivatives. The coefficients of the linear terms called also as flutter derivatives depend on the flow (wind) velocity. These coefficients are to be determined by the Monte Carlo method using the measured acceleration data. The obtained results are compared to the results determined by curve-fitting on the acceleration time-signal. The original (structural) damping and stiffness matrices can be modified by using the flutter derivatives since the equations of motion form a homogeneous linear differential equation system. Thus, we get effective damping and stiffness matrices. Flutter instability occurs when a harmonic solution satisfies the equations. The critical flow velocity which the system loses its stability at is also compared to the stability boundary of the analytical model based on Theodorsen's approach.