Divergence instability of a simply supported orthotropic composite shell reinforced in both axial and circumferential directions is considered. The shell is subject to an axial static load and to an action of an outside supersonic gas flow in the direction parallel to the shell axis. Two variants of the solution considered in the paper include discrete widely spaced stiffeners and closely spaced stiffeners; the latter case can be treated using a smeared stiffeners technique. It is proven that divergence instability of shells treated by smeared stiffeners technique can occur only if they are subject to axial compressive loads exceeding the static buckling value.