  A stationary wave pattern occurring in a flow of a two-component
Bose-Einstein condensate past an obstacle is studied. We consider the general
case of unequal velocities of two superfluid components. The Landau criterium
applied to the two-component system determines a certain region in the velocity
space in which superfluidity may take place. Stationary waves arise out of this
region, but under the additional condition that the relative velocity of the
components does not exceed some critical value. Under increase of the relative
velocity the spectrum of the excitations becomes complex valued and the
stationary wave pattern is broken. In case of equal velocities two sets of
stationary waves that correspond to the lower and the upper Bogolyubov mode can
arise. If one component flows and the other is at rest only one set of waves
may emerge. Two or even three interfere sets of waves may arise if the
velocities approximately of equal value and the angle between the velocities is
close to pi/2. In two latter cases the stationary waves correspond to the lower
mode and the densities of the components oscillate out-of-phase. The ratio of
amplitudes of the components in the stationary waves is computed. This quantity
depends on the relative velocity, is different for different sets of waves, and
varies along the crests of the waves. For the cases where two or three waves
interfere the density images are obtained.
