I don't think so. Spirit is bigger, with almost twice the revenue of NZ, and is competing in a very different market. Spirit pretty much has to participate given it's primarily flying US domestic market and everyone else there does. The other aspect is that the cost regime is completely different. For Spirit the cost of participation is fully tax deductible. For NZ it would be an external cost and is only deductible on US income, which is minimal. There is no bottom line benefit to NZ by participating as far as I can see. I would expect that it is purely a cost consideration for NZ; they simply won't spend money if they can avoid it or it adds nothing to their bottom line.