The Minimum Operational Network (MON) is the FAA's backup system for widespread GPS outages, comprising a downsized network of VORs and about 200 "MON airports" with non-GPS approaches. The MON ...

Area navigation using GPS has been around (for us) for about 30 years. Before that we did mostly the same thing using LORAN for a while. But, the National Airspace System was designed around VHF Omni- ...