The Minimum Operational Network (MON) is an FAA initiative designed as a ground-based backup navigation system for IFR aircraft in the event of a widespread GPS outage. The MON consists of a downsized ...

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- ...