1. A method for performing diagnostics for an engine using operational data for the engine, the method comprising the steps of: identifying an engine component as potentially being related to the operational data; calculating a component deviation from a first model, wherein the component deviation relates the engine component to an adjustment to the first model with respect to a variable of the first model, based at least in part on the operational data; and comparing the component deviation with a plurality of root cause deviation measures, each root cause deviation measure relating one of a plurality of potential root causes to the first model with respect to the variable of the first model.