Complaint from the service failure has a huge negative impact to the airlines, especially from front line area. Weak or badly managed service can take many years to revive it from the customers’ perception. Moreover, the effects of negativity can remain over time, especially when it is widespread and left unchallenged. The rate of diffusion of negative information increases dramatically through mass media, Internet, and word of mouth. Consequently, the time and effort taken toward creating a successful brand can be diminished very quickly as negative information reaches a large number of customers in a short period of time, resulting in substantial financial and market loss. This study, the researcher examined whether and how factors affecting service quality of Passenger Service Department in airlines. In this case, AirAsia (Thailand) has been selected for the study. For the low cost airlines industry in Thailand, there are three main players, which are AirAsia, Thailand (subsidiary of AirAsia), Nok Air (subsidiary of Thai Airways International), and One-Two-Go Airlines (subsidiary of Orient Thai). The three low cost airlines have similar: cut off unnecessary costs to lower the ticket fare, online ticket sales, variety of payment channels and quality service. Since most of their strategies are almost the same, there is only one factor that they can compete each other is service quality. With the reasons above, however, there are some personal and operational factors that affect their service quality. Therefore, The questions for this study are;  (1) what are the perceptions of AirAisa (Thailand) passengers towards the airlines ground services? (2) Have the personal and operational factors of Passenger Service Agent affected their service quality (SERVQUAL 5 Dimensions)?  (3) What are the needs of Passenger Service Agent?  While the objectives for this research are  (1) to identify what are the top 5 areas that got high percentage that do not meet passengers’ expectation regarding ground services.  (2) to identify problems, obstacles or factors (root causes) affecting the quality of service of Passenger Service Agent of AirAsia, Thailand. The outcome of this research is to contribute to AirAsia (Thailand) so that it can be used for their service improvement in Passenger Service Department.