Customer satisfaction in Iranian airlines has obsessed my mind for a long time, moreover losing market share by Iranian airlines and high competition by foreign airline companies in the airline market in Iran were the major motivation for such research .An important aspect of customer relationship management (CRM), is customer satisfaction. This research has been focused on CRM, customer satisfaction, expectation disconfirmation theory and the SERVQUAL instrument. As far as studied no similar and such comprehensive research has been conducted in the airline industry in Iran. This research is focusing on the customer point of view. Data collection was done on nine IranAir international routes during flight. Both theoretical and managerial implications were obtained from the study. The theoretical implication shows strong relationship between expectation disconfirmation and perceived performance which forms satisfaction. By this research, the expectation disconfirmation theory is confirmed in the airline industry. The most important and crucial managerial implication is that airlines with old aircraft fleet can still achieve customer satisfaction process, hence old aircraft fleet is just one factor of several factors influencing and determining customer satisfaction formation process, the highest priority which Iranian airlines have to focus on is the company’s responsiveness aspects regarding their customers.