A mathematical model to measure the level of service at airport passenger terminals is presented. The model relates passengers’ ratings of services at terminals and the time spent waiting for those services. The fuzzy concept is used to deal with the vagueness of service ratings such as “satisfied” and “unsatisfied.” Furthermore, two instruments are used to obtain the amount of time spent in service processes: perceived time reported by passengers and objective quantities measured by researchers. Empirical data reveal that the mean of perceived waiting/service time is significantly greater than the objective time in both check-in and baggageclaim processes, indicating that passengers tend to overestimate their time spent in each process. Furthermore, the amount of overestimation varies among service processes, with passengers having greater overestimations in both check-in service and baggage-claim waiting than in check-in waiting. These results imply that the two former processes are less tolerable than the latter one. The differences between those two measurements are further accentuated by the estimated level-of-service thresholds, with most thresholds based on subjective perceptions being greater than those based on objective measures. Estimation results also suggest that airport operators and airlines need more efforts to upgrade a service currently at higher service levels than at lower service levels.