WAC Bennett Dam was constructed between 1964 and 1967, with first filling occurring shortly after the completion of construction. Piezometers installed within the dam's core showed pore pressures and hydraulic gradients much higher than the predicted values assuming a constant permeability. Several different hypotheses were postulated for the cause of the high pore pressures, with the migration of trapped air, a process termed air-theory, identified as being partially responsible. Air theory involves water in the reservoir, under-saturated with respect to air, entering the core, dissolving air in the upstream part of the core and exsolving it towards the downstream side of the core. This creates a saturated and partially saturated zone within the core. The movement of the saturation front and the difference between the saturated and unsaturated permeability causes excess pore pressures to develop. This paper presents the development of a two-dimensional air-theory formulation in FLAC and the results of a two-dimensional simulation for two instrumented sections at WAC Bennett Dam. This model is an extension of previous one-dimensional efforts which modelled a simplified stratigraphy and one line of instruments at the base of the core, calibrated against laboratory and field data. The paper shows that the 2D air theory formulation can be used to better explain the observed high pore water pressures and gradients within dam cores before steady state seepage conditions are reached, and also discusses potential further physics to consider in conjunction with air theory.