In this paper, a simple theoretical model for the fractional air recovery to the concentrate in flotation froths is presented. The model assumes that two forces are exerted on the films, one from the curvature of Plateau borders and the other from the stretching of the films. It is further assumed that there is a critical pressure above which the films will fail. This model predicts that there is expected to be a maximum in the air recovery as the air rate is increased, which is indeed observed experimentally at a number of industrial flotation plants. This maximum in air recovery does not correspond to a maximum in the inherent stability of the films and occurs even if this stability is constant, though having a film stability that changes with air rate causes some interesting changes in the behaviour of the system. (C) 2008 Elsevier Ltd. All rights reserved.