The U.S. Army Engineer Research and Development Center (ERDC) is currently evaluating the performance of aluminum, fiberglass, plastic, and composite airfield mats under both F-15 and C-17 aircraft loads. Historically, the design methodology to determine the number of aircraft passes that a particular airfield mat will sustain before failure has been empirically correlated to the subgrade California Bearing Ratio (CBR) and the equivalent single-wheel load. A new mechanistic design approach was developed in which the performance of the airfield mat is related to the maximum deviatory stress being applied to the subgrade. New design criteria relating this deviatory stress to the number of passes for aircraft wheel loads were also developed. A new mat response model as well as comparisons to experimental measurements collected from full-scale traffic test sections conducted at the ERDC is presented in this paper to show the applicability of the new design procedure.