"Doug" wrote

You HAVE to have a backup to GPS and USE it. Some sort of non-GPS
system.

Doug...recently you are posting a lot about things that you
have no knowledge of.
In this case, you obviously have no knowledge of long-range
oceanic flying.
What would you suggest as a backup in the middle of the
Pacific Ocean?
It was not a GPS problem, it was a programing error that the
pilot did not detect.

Bob Moore
ATP CFI
PanAm (retired)