Wiggy:
Any error in the above processes, (e.g. in measuring the accelerations) will result in a mismatch between where the INS "thinks" you are and where you really are in the world.
In practical terms, in 1979 on a DC-10, is it reasonable then to suppose that this type of error was far more likely than a failure of a ground based navigation aide? I'm thinking the answer is "yes." But then I have heard from one pilot that AINS is "much more accurate" than what a typical ground based aide would predict for a plane's exact position. Maybe this is true also?