Steady two-layer thin-film planar flow under gravity is investigated theoretically in this study. The film is assumed to emerge out of a channel and flow over a straight plate. The interplay among inertia, viscous and surface or interfacial tension is emphasized. It is found that the film and interface profiles, as well as the flow field, are strongly influenced by the viscosity ratio, film thickness ratio at inception, and surface-to-interfacial tension ratio. In the absence of surface and interfacial tension, the profiles of the film layers vary monotonically streamwise. The surface tension effect leads to waviness in layer profiles, with increasing wave number as the surface tension effect is reduced.