Aeroelastic response of the small experimental supersonic transport (NEXST-1) at the 2nd flight experiment was examined. Two accelerometers were equipped on the main wings to monitor those aeroelastic responses. Dampings of the structural modes were obtained by the Random Decrement Technique. Although the damping of the symmetric first wing bending mode slightly reduced while the aircraft passed though the transonic regime, aeroelastic instability was not observed. It seems that the flow separation occurred at about two degrees of angle of attack and it excited the wing vibration. These data are reported in this paper.