Array detector based systems with statistical analysis capability integrated with real-time data acquisition can provide a wealth of spectral information from a variety of potentially useful gas phase emitting species. In the case of particularly challenging applications such as low-open area self-aligned contact (SAC) etches, utilization of the full optical emission spectrum has been shown to accurately detect endpoint when all other endpoint systems studied failed. Production facility results regarding these and other demanding applications will be presented. The talk will largely focus on oxide etching in AMAT MXP and TEL DRM platforms. Evolving Window Factor Analysis (EWFA) is the principal multivariate techniques used in the analysis. They allow one to dynamically track the principal components of the oxide etch process. EWFA is also shown to useful for automatic fault detection.