Almost all the expenses are borne by the FAA. The FAA is solely
responsible for navigation aids. And the trend is to GPS. NDBs are no
longer being maintained, and are being decommissioned at a rapid rate.
LOMs are becoming rare. And precision GPS approaches are now a reality,
if the proper equipment is installed in the aircraft. The approaches are
being published. GPS approaches are far more accurate than VOR
approaches, and the horizontal accuracy is at least as good as ILS
localizers. The FAA rather desperately wants to get away from the
requirement to maintain obsolete equipment at thousands of locations all
over the US. Eventually it will.
