During the past four decades, the Lewis Research Center has been providing advances in aeronautical propulsion from the research activities of its staff and its university and industrial grantees and contractors. These advances have helped create the preeminence in aeronautics that has contributed to our national defense, has provided swift and reliable transportation for our people and their goods, and has greatly aided our position in international trade. In recent years substantial resources have also been directed at improving our nation's utilization of energy. NASA is well aware that the aviation industry is an important segment of our national economy. In 1979 aircraft sales led all U.S. manufacturing industries with a trade surplus of over $10 billion - without which the country would have experienced a one-third greater trade deficit. This favorable balance attributable to the aircraft industry is largely a result of being able to provide a superior product and to continue to upgrade the product. Efforts at improving the performance retention of today's and future engines which will power commercial and military aircraft represent a positive step toward this end. To provide to representatives from government, industry, and universities the latest findings directly related to improved aircraft engine performance retention, a two-day conference was held in May 1981. This publication contains the papers presented at that conference.