In the FAQs for the flight planner, it states:
What is the service area of FlightAware flight planning? Do you support Hawaii and Alaska? (Back to top)
Currently we only support domestic US flights. We’re currently testing support for Alaska and Hawaii and we plan to extend support to Canada and the Caribbean in the future.
Can you change “domestic US flights” to “contiguous 48 states” or “lower 48 states” or “the states between Canada and Mexico”? It’s been a pet peeve of mine ever since I lived in Hawaii that people don’t consider Alaska or Hawaii to be domestic.