writes:

Accuracy isn't the problem. Would it be as reliable?
Would it be affordable and workable in airplanes that lack
electrical systems? And would it work when those
electrical systems failed?

In modern aircraft, a failure of electrical systems brings a lot more
problems than mere navigation errors. No radio, no other navaids, no
control surfaces in some aircraft, no propulsion in some aircraft.

And while a compass shows magnetic north, that's all it shows. You
have no idea how far north or south you are, or which direction to fly
to your destination.

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