GPS Irrelevant
GPS reception is not a factor in this accident. Dual or triple GPS are fed into the Fright Management System, along with triple IRU acceleration derived data. Planes crossed the oceans long before GPS with only Inertial Navigation Systems, and can still do it. In fact, the IRU provides a flywheel effect at critical times, as it is based on accelerations, whereas GPS is positionally derived, subtracting where you are from where you were.
Juneau Alaska has a particularly difficult approach and go around requirement. GPS and ground based navigation sensors are supplemented by IRU to provide that flywheel for navigating safely in the go around.
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