Abstract: To address the vulnerability of GNSS to interference and spoofing, as well as the insufficient resilience of a single positioning, navigation and timing (PNT) system, and to meet the demand for high-reliability PNT services in critical industries, we investigated the backup support role and upgrade directions of Enhanced Long-Range Navigation (eLoran) within the national comprehensive PNT system. Taking the regional navigation anomaly event in Nanjing as a case study, we reviewed the technical principles and development status of eLoran. We analyzed its key bottlenecks from five aspects: signal structure, broadcasting capability, system architecture, device ecosystem, and management mechanisms. We proposed an upgrade pathway oriented toward “ubiquitous coverage, security and trustworthiness, and demand-driven services” and constructed an integrated backup standard. The results show that eLoran possesses advantages of high anti-interference capability, heterogeneous redundancy, and independent timing, enabling it to provide continuous and reliable backup PNT services when GNSS fails. Moreover, its integration with BeiDou Navigation Satellite System (BDS) and communication networks can form a multi-source collaborative spatiotemporal service system. We conclude that eLoran is a key technology for enhancing the security resilience of the national PNT system, and its systematic construction and industrialization are of significant strategic importance for building modern spatiotemporal infrastructure.