[-] Extended Range Error

[Air Australia]

Converted L-1049C seating to 50/12/2 to enable non-stop range between Honolulu and Tokyo, however unable to allowcate aircraft to service as system saying aircraft does not have enough range to operate the service. Conversion should allow about 10% more than required.

[MikeS]

You need to take head winds into account. When opening a new route and assigning your aircraft you can hover over the question mark symbol next to each flight (outbound/inbound) and see the effective range needed with the prevailing winds.
In your case, probably the HNL-NRT sector will show a higher range demand than your aircraft has to offer.

Cheers!
Mike