Oscillations of rectangular cylinder elastically suspended in an air-flow were studied experimentally. The amplitude of oscillations measured at various cylinder lengths was shown to be affected by changes in incoming flow velocity and also by the presence or absence of end plates restricting the flow of air through the ends of the cylinder. Steady-state oscillation amplitude increases with an increase in cylinder aspect ratio. In the presence of end plates, the oscillation amplitude linearly depends on the Strouhal number. At the cylinder aspect ratio of five, the presence or absence of end plates on the cylinder has no effect on the oscillation amplitude.