This FAA interest stemmed from the Korean Air B747 crash at Guam
the only way the airline could continue flying and satisfy the FAA and CASA was to come under the Australian AOC system
I think you'll find, if my memory serves me correctly, that, at the time of the KAL crash at GUM, Air Nauru was already operating under an Australian AOC. Willing to be corrected, but worth checking to be sure ..............