An inkjet printhead including: an elongate fluid manifold comprising: an inlet boss, an outlet boss, a longitudinal channel extending between the inlet and outlet bosses, a plurality of air cavities positioned above the longitudinal channel in a roof cavity of the fluid manifold, and plurality of fluid outlets defined in a floor of the longitudinal channel; and a plurality of printhead chips attached to the base of the fluid manifold, each printhead chip receiving printing fluid from one or more fluid outlets. The air cavities are defined by ribs extending from a roof of the fluid manifold towards the longitudinal channel and each rib has a lip protruding beyond a lower surface of the inlet and outlet bosses.