Measurements of ozone, NO, NO₂, NO_y, CO, VOC, and SO₂ collected with the Baylor University Twin Otter aircraft during TexAQS 2000 were analyzed to better understand the source types that contributed NO_x (NO+NO₂) and VOC precursors to the ozone production observed. Source types were identified through analysis of SO₂/NO_y and CO/NO_y ratios observed. Also presented is an analysis of the effect of measurement uncertainties on the results.