my book says:
Maximum flight operating latitude - 82° North and 82° South, except for the region between 80° West and 130° West longitude, the maximum flight operating latitude is 70° North, and the region between 120° East and 160° East longitude, the maximum flight operating latitude is 60° South.
and
Air Data Inertial Reference Unit (ADIRU)
ADIRU alignment must not be attempted at latitudes greater than 78 degrees
15 minutes.