In my view, since the ADIRU will no longer have the SAIRU as a backup, what would happen if the ADIRU failed during flight? What would the FMS use to update the aircraft’s position?There must be at least one GPS receiver available.As for NAVAIDs along the route, their availability may not be reliable.And if the aircraft enters a jamming or spoofing area, having GPS would be of no use anyway. That is why flight operations are not permitted in such areas.