Engines are thrust producers for commercial aircrafts that enables to fly on air so that developing engines performance management system is essential factor so as to increase on wing performance of engines, therefore, it reduces system failures and maintenance costs. Having this fact in mind, this study aimed to investigate the effect of engine sector length, engine operational severity, engine phase (first and mature run), and engine maintenance cost on engine Time since last shop-visit (TSLSV). The study was performed selecting three out of ten engine models in Ethiopian Airlines using secondary data collected by the company under study. Exponential Reliability distribution method and Correlation analysis have been utilized to conduct the research. The result showed that the performance of the engines highly influenced by independent variables. The main objective of this research have been met through analyzing the existing system reliability of PW150, PW4000 and CFM56-7B engines operated by Ethiopian Airlines and engine performance monitoring and management system has been developed to extend engines on-wing longer. The contributions of the developed model has been observed through maximizing the reliability from 95.87%, 98.35% and 99.02% to 96.33%, 98.56% and 99.07% as well as minimizes the maintenance cost of $4,071,438.00, $8,934,600.24 and $6,073,539.84 for PW150, PW4000 and CFM56-7B engines respectively.