A method for assessing the impact of vehicle technologies and new aircraft concepts at the fleet level is presented. Various aspects of the method constitute a departure from standard practice intended to address known shortcomings and advance the state of the art. In particular, an operational activity growth routine is implemented where operational sets are grown to match top-level and airport-level forecasts that are fully balanced for all origin–destination airport pairs. The proposed approach also features a novel fleet evolution scheme where replacements are devised on the basis of mission capabilities for aircraft types rather than on seat classes, and the retirement of aircraft is applied to models introduced beyond the reference year. Surrogate models of fuel burn are regressed from gold-standard modeling tools and are shown to be suitable for system-wide assessments on the basis of model representation accuracy. Fleet assessment results are shown for various technology introduction and growth scenarios and indicate that an introduction of NASA vehicle technologies across the fleet in 2025 can yield up to 436: 05 109 kg of fuel savings through 2050, or up to 94.6 million additional operations for that same period assuming a 2050 total fuel-burn cap at 2006 levels.