Self-contained navigation has always been a priority in aviation, for fairly obvious reasons (safety, i.e. not having to depend on the complex external single point of failure that GNSSs are, and security, i.e. GNSS spoofing).

Planes were using INSs long before GPS to navigate across oceans, but even today, they're required to carry several instances of each (GPS and INS, in addition to ground-based systems) for redundancy.