There might be a very large metal deposit close to the surface (like in Sudbury) that upsets the local magnetic domain.
[0] - https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#d...
Flying a great-circle route that intersects the North Pole, and magnetic North Pole, would mean travelling both north and south at the same time for a period.
It's perhaps unfortunate that we live in an era where they are "close enough" that we have one word (North) for two different directions.
Is it possible for the magnetic poles to ever exist far from the geographic poles? (I know the magnetic field could have been the opposite polarity, or not existed at all, but in either of those cases, we still wouldn't have gotten another word.)
The north magnetic pole has been south of 70 degrees as recently as the mid-1800s and the south magnetic pole is currently north of 65 degrees. Every half million years or so the whole thing goes nuts for a while and reverses.
I don’t think the exact mechanics of the magnetic field are super certain, but the general idea is that the rotation sort of pins the poles nearish to the axis but there’s been some significant variation historically.