The pure fact that they are the only one that does fly the route. With United Hawaii can be reached from SFO, LAX, and DEN. Also the size and the amount of flights that they opperate allow them to feed into those flights in a better way than AA. If UAL flew the flight then both airlines would lose tons of money. While with only AA on the route, they can for the most part come close to breaking even.
that was a great response.
when i work the COS-LAX flts everyday,you would be surprised at how much the dollar values are for those flts.they are crap,mileage plus tkts galore and bulk tkts to boot.very rarely do you see a $value for a pax between these cities.
you should see the dollar value for pax going to SYD,AKL,NRT,PEK,HKG,AND inner china. $$$$$$$$$$ that is why they probably still fly the route for the asian pax and aussies.