I’ve been tracking many flights in the Hawaiian region since that is where I am based. The ICAO code for airports in the Pacific start with the letter P - for instance PHNL for Honolulu - instead of the standard K for continental USA.
One thing that I’ve noticed on FlightAware is that when I pilot files a flight plan using the FAA 3-letter ID in Hawaii, the letter K gets automatically added to the start of the ID by default. For instance, Hana, Maui is uses HNM for their ID. When a pilot files the plan, it shows up as KHNM. In reality it should be either PHNM or HNM.
I’ve noticed this slight problem with the following airports:
HNM - should be PHNM
NGF - should be PHNG
LUP - should be PHUP (I think)