<p>This paper considers stationary disturbances in the boundary layer stability equations for the variants of subsonic and supersonic flow past a plate. For a case of two-dimensional disturbances, theoretical results agree with the available literature data. For the first time, disturbances in a form of longitudinal structures were studied. It was found that the amplitudes of disturbances in longitudinal velocity and temperature over the boundary layer take a bell-shaped profile. This profile has the positions of maximum (in the Dorodnitsyn – Howarth coordinates) which are conservative to variations in the Mach number, Reynolds number and the spanwise wavenumber. Meanwhile, the rate of disturbance dumping along the transversal coordinate and disturbance phase shift over the boundary layer keeps growing with an increase in the listed parameters. The highest change in phase belongs to the lateral velocity parameter.</p>