Analytical and computer models are presented to predict the evolution of planar areas and transitional slopes micromachined in glass using abrasive jet micro-machining. The energy distributions across a rectangular and a round nozzle were found to be non-uniform and therefore unsuitable to machine flat surfaces in a single pass. Consequently, a simple model was developed to guide the computer-controlled machining of an approximately flat surface, by the use of multiple passes arranged in such a manner that the summation of their energy distributions gave a uniform energy flux to the surface. Planar areas were machined in glass, and there was good agreement between the model predictions and experimentally measured surface profiles. Masked planar areas were also machined, and it was found that particle scattering by the mask edge (Ghobeity, Krajac, Burzynski, Papini and Spelt 2008 Wear 264 185–98) caused the sidewalls of the planar area to be very shallow, on the order of only a few degrees. A novel method is presented to increase the slope at the edges of such masked planar areas. Although the methods are demonstrated through the micro-machining of flat, planar areas, they are equally applicable to the production of inclined planar areas and arbitrarily curved surfaces.