Originally Posted by
christep
Because if it's empty then the cost is minimal (no catering, probably one or two less crew), and if it's full of op-ups then they are getting, in effect, J-class revenue for those seats which they obviously value more highly than miles. CX sells AsiaMiles at about US$0.01, so for them an F reward HKG-JFK RT at 220,000 miles is only US$2,200. There are probably passengers in Economy paying more than that!
You can waitlist for First class award using Asia Miles anyway so CX does care about filling their front cabins. I think the poster in question is complaining about not being able to use AA miles on CX. I have seen that before but that's one of the few benefits of keeping & earning a handsome balance of Asia Miles / Marco Polo Club or else a lot of people would have moved to AAdvantage.