Interesting assessment considering that there are operators of new 767-300s A330s (charter operators), and newer 747-400s going into HNL, along with the 737-700s and -800s.
Just to point out that AA cost per seat mile on a 767 is something like 4 cents and they yield on average 8 cents a flight. The 757s do slightly better. US Airways has a lower cost per seat mile than AA does because, on average, they fly their A330s more per day. Also, it costs less for CO to run a 767-400 than a DC-10. UA Switched to a mix 767, 757, 777 fleet which operated at a lower cost than the older DC-10s. Therefore IMO, older aircraft are less likely to profitable on a low yield route.
--Based upon 2001 3Q Form 41 since most of the airlines operated their respective fleet types (with the one exception being the UA DC-10)
FF miles redemption is limited too. I know TW limited about 5% of its seats on Hawaii flights to FF miles, Students and Senior travel packs combined. It was about 9 seats on a 767. Sometimes booking at the max limit (something like 330 days) was not even enough time to get the student travel. The rest of the seats (200+) were sold at the higher fares and at travel agencies.
US would have problem just from the cost and travel time from the east coast. Most people would like to visit Hawaii and decide to go to Florida and Caribbean because it is cheaper and quicker. People lose almost 2 days off a vacation traveling to Hawaii from anywhere east of the Rockies. Including jet lag, why would anyone pick Hawaii over a closer, more affordable sunny destination.