Navigation systems are built on very conservative assumptions. They fall back to autonomous inertial guidance, if satellite and ground-based navigation aids bec

Navigation systems are built on very conservative assumptions. They fall back to autonomous inertial guidance, if satellite and ground-based navigation aids become unavailable. This reduces airspace throughput (airplanes need larger separation distances due to lower navigation accuracy), but is completely safe. See: https://aviation.stackexchange.com/a/2276 https://aviation.stackexchange.com/a/2276