The paper presents a methodology to measure the dynamic resiliency of a public transport network. Variability in service supply that arises from normal day-to-day service fluctuations leads to negative passenger experiences and therefore satisfaction. The paper explores the utilization of dynamic data to develop a systematic approach analysing disruption impacts with respect to service-wide capacity changes due to fleet failures. In order to measure the dynamic resilience, an index is formulated that covers the magnitude of changes in the network performances in terms of robustness, reliability, and residual capacity; measures that describe the network complexity in a physical and a service operational specification. In this regard, the relationship between system components is characterized by network topology, passenger flow, and service performance dynamics. Our proposed approach captures the dynamics of the resilient system and quantifies the extent to which operational strategies can deliver efficient systems. We illustrate our model by an application to the New Delhi bus transport system and demonstrate how system resiliency for different fleet-failure states can be quantified.