I quit fling almost 20 years ago and do not even read the periodicals anymore, but I am certain that as of yore the modern high performance aircraft have multiple systems.
Not just two of everything, but multiple nav systems.
Here is a link that gives an overview:
/http://www.aviainfo.gov.mv/downloads/operations/pbn/pbn_p1_c2.pdf
GPS is just a icing on the cake. You coud turn the GPS off and still navigate to any point in the world and land on a CAT II or III airport.
That link looks strange, so a short note.
Most all modern aircraft have nav systems known as VOR, Distance masuring, Loran, and the old standby, ADF
The big iron will have inertial navigation systems and inertial reference systems.
There are several more, but this makes the point.
Plus even with total nav system failure, there is ATC radar and excellent ratio communication between the controllers and the aircraft....and military airports can put the wheels on the runway with radar and pilot communication only and can do so when the ducks are afraid to even walk.
The guy that wrote the article has no idea what he is talking about in-so-far as aviation goes.
re: “Most all modern aircraft have nav systems known as VOR, Distance masuring, Loran, and the old standby, ADF”
Gotcha there; ADFs are just about totally gone. LORAN C has been history for awhile now. There was thoughts of bringing back LORAN C in a limited form, but I don’t think that has materialized beyond some tests 7 - 8 years back.
Absolutely, aircraft do have multiple systems. If the GPS goes bad, it’s not like they’re just flying around lost. Even if a plane lost all nav systems, the ground controllers still have radar and could talk them in.