We present an analysis of an electrostatic MEMS squeezefilm dominated drop ejector. The MEMS ejector consists of a microfluidic chamber, an orifice plate, and an electrostatically driven piston positioned a few microns beneath the orifice. The piston is supported by cantilevered flexural members that act as restoring springs. To eject a drop, a voltage is applied between the orifice plate and the piston, which produces an electrostatic force that moves the piston towards the nozzle. The moving piston generates a squeeze-film pressure distribution in the gap region above it that acts to eject the drop. A prototype MEMS drop ejector has been fabricated and characterized at Sandia National Laboratories. In this presentation, we discuss the operating physics of this device, and simulate its performance using both coupled fluid/structure CFD analysis and a lumped-element electromechanical model. We study key performance parameters such as piston displacement and pressure generation.