To ensure the normal operation of the airport terminal system, the impact of redundancy on operation resilience was analyzed by taking incidents such as security checkpoint failures and staff absenteeism at check-in counters as examples. A definition and quantification method for resilience, covering the entire process from system disruption to recovery, was proposed. T1 terminal of a major airport handling tens of millions of passengers annually was selected as a case study. An operation model of the terminal was constructed based on Anylogic. The influence of the number of security checkpoint failures, failure duration, recovery measure intensity, and the number of absent staff at manual check-in counters on terminal operation resilience was analyzed under scenarios with and without redundancy. The results indicate that when the system redundancy is lacking, the operation resilience of the terminal decreases as the number of security checkpoint failures and absent staff increases, shows no significant correlation with failure duration, but improves with the enhancement of recovery measure intensity. In contrast, when the system incorporates redundancy, the functional level either remains unaffected or declines less significantly compared to the non-redundant scenario, and the system resilience is higher. Moreover, if the system possesses redundancy and the redundancy degree exceeds the disruption intensity, the functional level remains unchanged, and the system resilience approaches 1.0. Therefore, redundancy is a critical factor that cannot be overlooked in resilience analysis.