A theoretical analysis of the fluid mechanics of the air cushion of the air reversers used in web-handling systems is presented. A two-dimensional model of the air flow obtained by averaging the equations of conservation of mass and momentum over the clearance between the web and the reverser is solved numerically. The effect of the pressure holes in the surface of the air reverser are represented by nonlinear source terms in the modified Euler’s and mass conservation equations. The results of the numerical solution axe compared with a 1D analytical solution of these equations, an empirical formula and the one-dimensional air-jet theory developed for hovercraft. Conditions that maximize the air pressure supporting the web are analyzed and design guidelines are deduced.