|NASA's Environmentally Responsive Aviation Project (ERA) is working with the industry to develop the combustor technologies for a new generation of low-emissions engines targeted for the 2020 timeframe. These new combustors will reduce Nitrogen Oxide (NOx) emissions to half of current State-of-the-Art (SOA) combustors, while simultaneously reduce particulate emissions. NASA has been driving the NOx reduction effort in the aviation industry over the last four decades , resulting in approximately 50% reduction every generation of about 15 years (Figure 1). The initial concerns were health issues such as ground-level NOx and its contribution to photochemical smog. As a result, a series of increasingly stringent NOx emission standards by the International Civil Aviation Organizationâs (ICAO) Committee on Aviation Environmental Protection (CAEP) have, over the years, regulated aviation emissions below 3,000-foot altitude. These standards cover the take-off, climb, descent, and taxing/ground idle phases of the engine operation, the socalled Landing and Take-Off (LTO) cycle, in a prorated fashion. With forward-thinking research, the aviation propulsion industry has turned these past NASA-sponsored combustor concepts into flight hardware.